Era sekarang ini merupakan masa dari jaringan wireless, baik yang dipasang di rumah ataupun di kantor. Walaupun tekhnologi wireless sangat berguna, namun bukan berarti tanpa masalah. Beberapa masalah yang dialami biasanya berkaitan dengan manajer jaringan atau alamat jaringan, atau keamanan Wi-Fi. Ketika menggunakan computer tanpa jaringan Wi-Fi yang aman, dapat membawa Anda ke masalah yang dinamakan pembajakan bandwith.
Untuk mengantisipasi hal ini, maka Anda memang harus mengikuti instruksi yang ada ketika menginstal jaringan Wi-Fi ke komputernya. Jika instalasi sudah benar, maka user Internet lain yang tidak sah akan diblokir ketika akan masuk ke jaringan Wi-Fi Anda. Untuk membuat jaringan Wi-Fi lebih aman, maka Anda dapat menggunakan tekhnologi enkripsi, namun harus tetap berhati-hati, walaupun sudah ada ukuran enkripsi WPA2 (yang sering digunakan kebanyakan user) dan WEP. Enkripsi data di jaringan Wi-Fi bertujuan agar tidak ada seorang pun yang dapat membaca data Anda di jaringan. Ketika menggunakan jaringan wireless, keamanan Wi-Fi adalah hal utama yang perlu diperhatikan. Ketika semua persiapan jaringan Wi-Fi sudah benar, maka Anda dapat menggunakan jaringan wireless dengan mudah dan damai.
Masih ada kemungkinan untuk Anda yang menggunakan jaringan wireless, sebaiknya mewaspadai tekhnologi penting yang dapat jatuh ke tangan hacker dari perusahan competitor. Oleh karena itu, keamanan personal data menjadi hal utama dari jaringan Wi-Fi. Isu keamanan Wi-Fi ini berkaitan dengan tekhnologi plug and play. Jadi, ketika Anda mungkin lengah atau tidak berhati-hati, ada seseorang di dekat base station Anda, yang dapat mengganggu data yang diterima dan dikirim dari jaringan Anda atau dapat membuat system juga ikut tergangu. Masalah tersebut muncul ketika men-setting Wi-Fi hotspot baik di kantor, di rumah, atau di public hotspot.
Telepon Wi-Fi adalah sebuah alat yang dapat digunakan untuk koneksi wireless agar menghemat biaya pangilan telepon. Wi-Fi phone dapat digunakan dalam radius 90 m tanpa adanya gangguan dalam hotspot. Selain itu, juga tergantung dengan jumlah orang yang mengakses Wi-Fi hotspot dalam waktu tertentu. Sebagian besar router memiliki layanan identifikasi autentikasi user, namun hacker sudah familiar dengan protocol yang digunakan di router. Anda dapat mempertimbangkam untuk mengubah password ke yang lebih sulit dan tidak mudah ditebak, atau mungkin Anda dapat mengganti password secara periodic.
Perusahaan yang menggunakan system remote access point dan interface web sebaiknya menggunakan protocol keamanan dan password untuk jalan akses sebaiknya diganti sesering mungkin. Mungkin Anda juga dapat mempertimbangkan untuk menghapus data di hardware yang tidak digunakan, karena hal ini akan mencegah adanya kemungkinaan kejahatan financial, pencurian identitas atau akes ke system computer. Selain itu, software Wi-Fi security dapat diinstal di semua alat WI-Fi
sumber : beritanet.com
Tips-tips wireless security
Pendahuluan
Jaringan nirkabel atau yang sering disebut dengan wireless network cukup mudah untuk di set up, dan juga terasa sangat nyaman, terutama jika kita menginginkan agar bisa berjalan jalan keliling rumah atau kantor dengan komputer portable tetapi tetap bisa tetap mengakses jaringan internet. Namun, karena wireless menggunakan gelombang, maka akan lebih mudah untuk di-hack daripada koneksi yang menggunakan kabel. Ada beberapa tips disini untuk mengamankan wireless network.
Isi
Adapun langkah langkahnya sebagai berikut
1. Memakai enkripsi.
Enkripsi adalah ukuran security yang pertama, tetapi banyak wireless access points (WAPs) tidak menggunakan enkripsi sebagai defaultnya. Meskipun banyak WAP telah memiliki Wired Equivalent Privacy (WEP) protocol, tetapi secara default tidak diaktifkan. WEP memang mempunyai beberapa lubang di securitynya, dan seorang hacker yang berpengalaman pasti dapat membukanya, tetapi itu masih tetap lebih baik daripada tidak ada enkripsi sama sekali. Pastikan untuk men-set metode WEP authentication dengan “shared key” daripada “open system”. Untuk “open system”, dia tidak meng-encrypt data, tetapi hanya melakukan otentifikasi client. Ubah WEP key sesering mungkin, dan pakai 128-bit WEP dibandingkan dengan yang 40-bit.
2. Gunakan enkripsi yang kuat.
Karena kelemahan kelemahan yang ada di WEP, maka dianjurkan untuk menggunakan Wi-Fi Protected Access (WPA) juga. Untuk memakai WPA, WAP harus men-supportnya. Sisi client juga harus dapat men-support WPA tsb.
3. Ganti default password administrator.
Kebanyakan pabrik menggunakan password administrasi yang sama untuk semua WAP produk mereka. Default password tersebut umumnya sudah diketahui oleh para hacker, yang nantinya dapat menggunakannya untuk merubah setting di WAP anda. Hal pertama yang harus dilakukan dalam konfigurasi WAP adalah mengganti password default tsb. Gunakan paling tidak 8 karakter, kombinasi antara huruf dan angka, dan tidak menggunakan kata kata yang ada dalam kamus.
4. Matikan SSID Broadcasting.
Service Set Identifier (SSID) adalah nama dari wireless network kita. Secara default, SSID dari WAP akan di broadcast. Hal ini akan membuat user mudah untuk menemukan network tsb, karena SSID akan muncul dalam daftar available networks yang ada pada wireless client. Jika SSID dimatikan, user harus mengetahui lebih dahulu SSID-nya agak dapat terkoneksi dengan network tsb.
5. Matikan WAP saat tidak dipakai.
Cara yang satu ini kelihatannya sangat simpel, tetapi beberapa perusahaan atau individual melakukannya. Jika kita mempunyai user yang hanya terkoneksi pada saat saat tertentu saja, tidak ada alasan untuk menjalankan wireless network setiap saat dan menyediakan kesempatan bagi intruder untuk melaksanakan niat jahatnya. Kita dapat mematikan access point pada saat tidak dipakai.
6. Ubah default SSID.
Pabrik menyediakan default SSID. Kegunaan dari mematikan broadcast SSID adalah untuk mencegah orang lain tahu nama dari network kita, tetapi jika masih memakai default SSID, tidak akan sulit untuk menerka SSID dari network kita.
7. Memakai MAC filtering.
Kebanyakan WAP (bukan yang murah murah tentunya) akan memperbolehkan kita memakai filter media access control (MAC). Ini artinya kita dapat membuat “white list” dari computer computer yang boleh mengakses wireless network kita, berdasarkan dari MAC atau alamat fisik yang ada di network card masing masing pc. Koneksi dari MAC yang tidak ada dalam list akan ditolak.
Metode ini tidak selamanya aman, karena masih mungkin bagi seorang hacker melakukan sniffing paket yang kita transmit via wireless network dan mendapatkan MAC address yang valid dari salah satu user, dan kemudian menggunakannya untuk melakukan spoof. Tetapi MAC filtering akan membuat kesulitan seorang intruder yang masih belum jago jago banget.
8. Mengisolasi wireless network dari LAN.
Untuk memproteksi internal network kabel dari ancaman yang datang dari wireless network, perlu kiranya dibuat wireless DMZ atau perimeter network yang mengisolasi dari LAN. Artinya adalah memasang firewall antara wireless network dan LAN.
Dan untuk wireless client yang membutuhkan akses ke internal network, dia haruslah melakukan otentifikasi dahulu dengan RAS server atau menggunakan VPN. Hal ini menyediakan extra layer untuk proteksi.
9. Mengontrol signal wireless
802.11b WAP memancarkan gelombang sampai dengan kira kira 300 feet. Tetapi jarak ini dapat ditambahkan dengan cara mengganti antenna dengan yang lebih bagus. Dengan memakai high gain antena, kita bisa mendapatkan jarak yang lebih jauh. Directional antenna akan memancarkan sinyal ke arah tertentu, dan pancarannya tidak melingkar seperti yang terjadi di antenna omnidirectional yang biasanya terdapat pada paket WAP setandard. Selain itu, dengan memilih antena yang sesuai, kita dapat mengontrol jarak sinyal dan arahnya untuk melindungi diri dari intruder. Sebagai tambahan, ada beberapa WAP yang bisa di setting kekuatan sinyal dan arahnya melalui config WAP tsb.
10. Memancarkan gelombang pada frequensi yang berbeda.
Salah satu cara untuk bersembunyi dari hacker yang biasanya memakai teknologi 802.11b/g yang lebih populer adalah dengan memakai 802.11a. Karena 802.11a bekerja pada frekwensi yang berbeda (yaitu di frekwensi 5 GHz), NIC yang di desain untuk bekerja pada teknologi yang populer tidak akan dapat menangkap sinyal tsb.
Senin, 26 Oktober 2009
Pronoun
A pronoun can replace a noun or another pronoun. You use pronouns like "he," "which," "none," and "you" to make your sentences less cumbersome and less repetitive.
Grammarians classify pronouns into several types, including the personal pronoun, the demonstrative pronoun, the interrogative pronoun, the indefinite pronoun, the relative pronoun, the reflexive pronoun, and the intensive pronoun.
Personal Pronouns
A personal pronoun refers to a specific person or thing and changes its form to indicate person, number, gender, and case.
Subjective Personal Pronouns
A subjective personal pronoun indicates that the pronoun is acting as the subject of the sentence. The subjective personal pronouns are "I," "you," "she," "he," "it," "we," "you," "they."
In the following sentences, each of the highlighted words is a subjective personal pronoun and acts as the subject of the sentence:
I was glad to find the bus pass in the bottom of the green knapsack.
You are surely the strangest child I have ever met.
He stole the selkie's skin and forced her to live with him.
When she was a young woman, she earned her living as a coal miner.
After many years, they returned to their homeland.
We will meet at the library at 3:30 p.m.
It is on the counter.
Are you the delegates from Malagawatch?
Objective Personal Pronouns
An objective personal pronoun indicates that the pronoun is acting as an object of a verb, compound verb, preposition, or infinitive phrase. The objective personal pronouns are: "me," "you," "her," "him," "it," "us," "you," and "them."
In the following sentences, each of the highlighted words is an objective personal pronoun:
Seamus stole the selkie's skin and forced her to live with him.
The objective personal pronoun "her" is the direct object of the verb "forced" and the objective personal pronoun "him" is the object of the preposition "with."
After reading the pamphlet, Judy threw it into the garbage can.
The pronoun "it" is the direct object of the verb "threw."
The agitated assistant stood up and faced the angry delegates and said, "Our leader will address you in five minutes."
In this sentence, the pronoun "you" is the direct object of the verb "address."
Deborah and Roberta will meet us at the newest café in the market.
Here the objective personal pronoun "us" is the direct object of the compound verb "will meet."
Give the list to me.
Here the objective personal pronoun "me" is the object of the preposition "to."
I'm not sure that my contact will talk to you.
Similarly in this example, the objective personal pronoun "you" is the object of the preposition "to."
Christopher was surprised to see her at the drag races.
Here the objective personal pronoun "her" is the object of the infinitive phrase "to see."
Possessive Personal Pronouns
A possessive pronoun indicates that the pronoun is acting as a marker of possession and defines who owns a particular object or person. The possessive personal pronouns are "mine," "yours," "hers," "his," "its," "ours," and "theirs." Note that possessive personal pronouns are very similar to possessive adjectives like "my," "her," and "their."
In each of the following sentences, the highlighted word is a possessive personal pronoun:
The smallest gift is mine.
Here the possessive pronoun "mine" functions as a subject complement.
This is yours.
Here too the possessive pronoun "yours" functions as a subject complement.
His is on the kitchen counter.
In this example, the possessive pronoun "his" acts as the subject of the sentence.
Theirs will be delivered tomorrow.
In this sentence, the possessive pronoun "theirs" is the subject of the sentence.
Ours is the green one on the corner.
Here too the possessive pronoun "ours" function as the subject of the sentence.
Demonstrative Pronouns
A demonstrative pronoun points to and identifies a noun or a pronoun. "This" and "these" refer to things that are nearby either in space or in time, while "that" and "those" refer to things that are farther away in space or time.
The demonstrative pronouns are "this," "that," "these," and "those." "This" and "that" are used to refer to singular nouns or noun phrasesand "these" and "those" are used to refer to plural nouns and noun phrases. Note that the demonstrative pronouns are identical todemonstrative adjectives, though, obviously, you use them differently. It is also important to note that "that" can also be used as a relative pronoun.
In the following sentences, each of the highlighted words is a demonstrative pronoun:
This must not continue.
Here "this" is used as the subject of the compound verb "must not continue."
This is puny; that is the tree I want.
In this example "this" is used as subject and refers to something close to the speaker. The demonstrative pronoun "that" is also a subject but refers to something farther away from the speaker.
Three customers wanted these.
Here "these" is the direct object of the verb "wanted."
Interrogative Pronouns
An interrogative pronoun is used to ask questions. The interrogative pronouns are "who," "whom," "which," "what" and the compounds formed with the suffix "ever" ("whoever," "whomever," "whichever," and "whatever"). Note that either "which" or "what" can also be used as an interrogative adjective, and that "who," "whom," or "which" can also be used as a relative pronoun.
You will find "who," "whom," and occasionally "which" used to refer to people, and "which" and "what" used to refer to things and to animals.
"Who" acts as the subject of a verb, while "whom" acts as the object of a verb, preposition, or a verbal.
The highlighted word in each of the following sentences is an interrogative pronoun:
Which wants to see the dentist first?
"Which" is the subject of the sentence.
Who wrote the novel Rockbound?
Similarly "who" is the subject of the sentence.
Whom do you think we should invite?
In this sentence, "whom" is the object of the verb "invite."
To whom do you wish to speak?
Here the interrogative pronoun "whom " is the object of the preposition "to."
Who will meet the delegates at the train station?
In this sentence, the interrogative pronoun "who" is the subject of the compound verb "will meet."
To whom did you give the paper?
In this example the interrogative pronoun "whom" is the object of the preposition "to."
What did she say?
Here the interrogative pronoun "what" is the direct object of the verb "say."
Relative Pronouns
You can use a relative pronoun is used to link one phrase or clauseto another phrase or clause. The relative pronouns are "who," "whom," "that," and "which." The compounds "whoever," "whomever," and "whichever" are also relative pronouns.
You can use the relative pronouns "who" and "whoever" to refer to the subject of a clause or sentence, and "whom" and "whomever" to refer to the objects of a verb, a verbal or a preposition.
In each of the following sentences, the highlighted word is a relative pronoun.
You may invite whomever you like to the party.
The relative pronoun "whomever" is the direct object of the compound verb "may invite."
The candidate who wins the greatest popular vote is not always elected.
In this sentence, the relative pronoun is the subject of the verb "wins" and introduces the subordinate clause "who wins the greatest popular vote." This subordinate clause acts as an adjective modifying "candidate."
In a time of crisis, the manager asks the workers whom she believes to be the most efficient to arrive an hour earlier than usual.
In this sentence "whom" is the direct object of the verb "believes" and introduces the subordinate clause "whom she believes to be the most efficient". This subordinate clause modifies the noun "workers."
Whoever broke the window will have to replace it.
Here "whoever" functions as the subject of the verb "broke."
The crate which was left in the corridor has now been moved into the storage closet.
In this example "which" acts as the subject of the compound verb "was left" and introduces the subordinate clause "which was left in the corridor." The subordinate clause acts as an adjective modifying the noun "crate."
I will read whichever manuscript arrives first.
Here "whichever" modifies the noun "manuscript" and introduces the subordinate clause "whichever manuscript arrives first." The subordinate clause functions as the direct object of the compound verb "will read."
Indefinite Pronouns
An indefinite pronoun is a pronoun referring to an identifiable but not specified person or thing. An indefinite pronoun conveys the idea of all, any, none, or some.
The most common indefinite pronouns are "all," "another," "any," "anybody," "anyone," "anything," "each," "everybody," "everyone," "everything," "few," "many," "nobody," "none," "one," "several," "some," "somebody," and "someone." Note that some indefinite pronouns can also be used as indefinite adjectives.
The highlighted words in the following sentences are indefinite pronouns:
Many were invited to the lunch but only twelve showed up.
Here "many" acts as the subject of the compound verb "were invited."
The office had been searched and everything was thrown onto the floor.
In this example, "everything" acts as a subject of the compound verb "was thrown."
We donated everything we found in the attic to the woman's shelter garage sale.
In this sentence, "everything" is the direct object of theverb "donated."
Although they looked everywhere for extra copies of the magazine, they found none.
Here too the indefinite pronoun functions as a direct object: "none" is the direct object of "found."
Make sure you give everyone a copy of the amended bylaws.
In this example, "everyone" is the indirect object of the verb "give" -- the direct object is the noun phrase "a copy of the amended bylaws."
Give a registration package to each.
Here "each" is the object of the preposition "to."
Reflexive Pronouns
You can use a reflexive pronoun to refer back to the subject of the clause or sentence.
The reflexive pronouns are "myself," "yourself," "herself," "himself," "itself," "ourselves," "yourselves," and "themselves." Note each of these can also act as an intensive pronoun.
Each of the highlighted words in the following sentences is a reflexive pronoun:
Diabetics give themselves insulin shots several times a day.
The Dean often does the photocopying herself so that the secretaries can do more important work.
After the party, I asked myself why I had faxed invitations to everyone in my office building.
Richard usually remembered to send a copy of his e-mail tohimself.
Although the landlord promised to paint the apartment, we ended up doing it ourselves.
Intensive Pronouns
An intensive pronoun is a pronoun used to emphasise its antecedent. Intensive pronouns are identical in form to reflexive pronouns.
The highlighted words in the following sentences are intensive pronouns:
I myself believe that aliens should abduct my sister.
The Prime Minister himself said that he would lower taxes.
They themselves promised to come to the party even though they had a final exam at the same time.
Personal pronouns, Possessive determiners, Possessive pronouns
Personal pronouns Possessive determiners Possessive pronouns
as subject
(nominative) as object
(accusative and dative)
I me my mine
you you your yours
he him his his
she her her hers
it it its its
we us our ours
you you your yours
they them their theirs
1 2 3 4
We have some books. The books are for us. These are our books. The books are ours.
Grammarians classify pronouns into several types, including the personal pronoun, the demonstrative pronoun, the interrogative pronoun, the indefinite pronoun, the relative pronoun, the reflexive pronoun, and the intensive pronoun.
Personal Pronouns
A personal pronoun refers to a specific person or thing and changes its form to indicate person, number, gender, and case.
Subjective Personal Pronouns
A subjective personal pronoun indicates that the pronoun is acting as the subject of the sentence. The subjective personal pronouns are "I," "you," "she," "he," "it," "we," "you," "they."
In the following sentences, each of the highlighted words is a subjective personal pronoun and acts as the subject of the sentence:
I was glad to find the bus pass in the bottom of the green knapsack.
You are surely the strangest child I have ever met.
He stole the selkie's skin and forced her to live with him.
When she was a young woman, she earned her living as a coal miner.
After many years, they returned to their homeland.
We will meet at the library at 3:30 p.m.
It is on the counter.
Are you the delegates from Malagawatch?
Objective Personal Pronouns
An objective personal pronoun indicates that the pronoun is acting as an object of a verb, compound verb, preposition, or infinitive phrase. The objective personal pronouns are: "me," "you," "her," "him," "it," "us," "you," and "them."
In the following sentences, each of the highlighted words is an objective personal pronoun:
Seamus stole the selkie's skin and forced her to live with him.
The objective personal pronoun "her" is the direct object of the verb "forced" and the objective personal pronoun "him" is the object of the preposition "with."
After reading the pamphlet, Judy threw it into the garbage can.
The pronoun "it" is the direct object of the verb "threw."
The agitated assistant stood up and faced the angry delegates and said, "Our leader will address you in five minutes."
In this sentence, the pronoun "you" is the direct object of the verb "address."
Deborah and Roberta will meet us at the newest café in the market.
Here the objective personal pronoun "us" is the direct object of the compound verb "will meet."
Give the list to me.
Here the objective personal pronoun "me" is the object of the preposition "to."
I'm not sure that my contact will talk to you.
Similarly in this example, the objective personal pronoun "you" is the object of the preposition "to."
Christopher was surprised to see her at the drag races.
Here the objective personal pronoun "her" is the object of the infinitive phrase "to see."
Possessive Personal Pronouns
A possessive pronoun indicates that the pronoun is acting as a marker of possession and defines who owns a particular object or person. The possessive personal pronouns are "mine," "yours," "hers," "his," "its," "ours," and "theirs." Note that possessive personal pronouns are very similar to possessive adjectives like "my," "her," and "their."
In each of the following sentences, the highlighted word is a possessive personal pronoun:
The smallest gift is mine.
Here the possessive pronoun "mine" functions as a subject complement.
This is yours.
Here too the possessive pronoun "yours" functions as a subject complement.
His is on the kitchen counter.
In this example, the possessive pronoun "his" acts as the subject of the sentence.
Theirs will be delivered tomorrow.
In this sentence, the possessive pronoun "theirs" is the subject of the sentence.
Ours is the green one on the corner.
Here too the possessive pronoun "ours" function as the subject of the sentence.
Demonstrative Pronouns
A demonstrative pronoun points to and identifies a noun or a pronoun. "This" and "these" refer to things that are nearby either in space or in time, while "that" and "those" refer to things that are farther away in space or time.
The demonstrative pronouns are "this," "that," "these," and "those." "This" and "that" are used to refer to singular nouns or noun phrasesand "these" and "those" are used to refer to plural nouns and noun phrases. Note that the demonstrative pronouns are identical todemonstrative adjectives, though, obviously, you use them differently. It is also important to note that "that" can also be used as a relative pronoun.
In the following sentences, each of the highlighted words is a demonstrative pronoun:
This must not continue.
Here "this" is used as the subject of the compound verb "must not continue."
This is puny; that is the tree I want.
In this example "this" is used as subject and refers to something close to the speaker. The demonstrative pronoun "that" is also a subject but refers to something farther away from the speaker.
Three customers wanted these.
Here "these" is the direct object of the verb "wanted."
Interrogative Pronouns
An interrogative pronoun is used to ask questions. The interrogative pronouns are "who," "whom," "which," "what" and the compounds formed with the suffix "ever" ("whoever," "whomever," "whichever," and "whatever"). Note that either "which" or "what" can also be used as an interrogative adjective, and that "who," "whom," or "which" can also be used as a relative pronoun.
You will find "who," "whom," and occasionally "which" used to refer to people, and "which" and "what" used to refer to things and to animals.
"Who" acts as the subject of a verb, while "whom" acts as the object of a verb, preposition, or a verbal.
The highlighted word in each of the following sentences is an interrogative pronoun:
Which wants to see the dentist first?
"Which" is the subject of the sentence.
Who wrote the novel Rockbound?
Similarly "who" is the subject of the sentence.
Whom do you think we should invite?
In this sentence, "whom" is the object of the verb "invite."
To whom do you wish to speak?
Here the interrogative pronoun "whom " is the object of the preposition "to."
Who will meet the delegates at the train station?
In this sentence, the interrogative pronoun "who" is the subject of the compound verb "will meet."
To whom did you give the paper?
In this example the interrogative pronoun "whom" is the object of the preposition "to."
What did she say?
Here the interrogative pronoun "what" is the direct object of the verb "say."
Relative Pronouns
You can use a relative pronoun is used to link one phrase or clauseto another phrase or clause. The relative pronouns are "who," "whom," "that," and "which." The compounds "whoever," "whomever," and "whichever" are also relative pronouns.
You can use the relative pronouns "who" and "whoever" to refer to the subject of a clause or sentence, and "whom" and "whomever" to refer to the objects of a verb, a verbal or a preposition.
In each of the following sentences, the highlighted word is a relative pronoun.
You may invite whomever you like to the party.
The relative pronoun "whomever" is the direct object of the compound verb "may invite."
The candidate who wins the greatest popular vote is not always elected.
In this sentence, the relative pronoun is the subject of the verb "wins" and introduces the subordinate clause "who wins the greatest popular vote." This subordinate clause acts as an adjective modifying "candidate."
In a time of crisis, the manager asks the workers whom she believes to be the most efficient to arrive an hour earlier than usual.
In this sentence "whom" is the direct object of the verb "believes" and introduces the subordinate clause "whom she believes to be the most efficient". This subordinate clause modifies the noun "workers."
Whoever broke the window will have to replace it.
Here "whoever" functions as the subject of the verb "broke."
The crate which was left in the corridor has now been moved into the storage closet.
In this example "which" acts as the subject of the compound verb "was left" and introduces the subordinate clause "which was left in the corridor." The subordinate clause acts as an adjective modifying the noun "crate."
I will read whichever manuscript arrives first.
Here "whichever" modifies the noun "manuscript" and introduces the subordinate clause "whichever manuscript arrives first." The subordinate clause functions as the direct object of the compound verb "will read."
Indefinite Pronouns
An indefinite pronoun is a pronoun referring to an identifiable but not specified person or thing. An indefinite pronoun conveys the idea of all, any, none, or some.
The most common indefinite pronouns are "all," "another," "any," "anybody," "anyone," "anything," "each," "everybody," "everyone," "everything," "few," "many," "nobody," "none," "one," "several," "some," "somebody," and "someone." Note that some indefinite pronouns can also be used as indefinite adjectives.
The highlighted words in the following sentences are indefinite pronouns:
Many were invited to the lunch but only twelve showed up.
Here "many" acts as the subject of the compound verb "were invited."
The office had been searched and everything was thrown onto the floor.
In this example, "everything" acts as a subject of the compound verb "was thrown."
We donated everything we found in the attic to the woman's shelter garage sale.
In this sentence, "everything" is the direct object of theverb "donated."
Although they looked everywhere for extra copies of the magazine, they found none.
Here too the indefinite pronoun functions as a direct object: "none" is the direct object of "found."
Make sure you give everyone a copy of the amended bylaws.
In this example, "everyone" is the indirect object of the verb "give" -- the direct object is the noun phrase "a copy of the amended bylaws."
Give a registration package to each.
Here "each" is the object of the preposition "to."
Reflexive Pronouns
You can use a reflexive pronoun to refer back to the subject of the clause or sentence.
The reflexive pronouns are "myself," "yourself," "herself," "himself," "itself," "ourselves," "yourselves," and "themselves." Note each of these can also act as an intensive pronoun.
Each of the highlighted words in the following sentences is a reflexive pronoun:
Diabetics give themselves insulin shots several times a day.
The Dean often does the photocopying herself so that the secretaries can do more important work.
After the party, I asked myself why I had faxed invitations to everyone in my office building.
Richard usually remembered to send a copy of his e-mail tohimself.
Although the landlord promised to paint the apartment, we ended up doing it ourselves.
Intensive Pronouns
An intensive pronoun is a pronoun used to emphasise its antecedent. Intensive pronouns are identical in form to reflexive pronouns.
The highlighted words in the following sentences are intensive pronouns:
I myself believe that aliens should abduct my sister.
The Prime Minister himself said that he would lower taxes.
They themselves promised to come to the party even though they had a final exam at the same time.
Personal pronouns, Possessive determiners, Possessive pronouns
Personal pronouns Possessive determiners Possessive pronouns
as subject
(nominative) as object
(accusative and dative)
I me my mine
you you your yours
he him his his
she her her hers
it it its its
we us our ours
you you your yours
they them their theirs
1 2 3 4
We have some books. The books are for us. These are our books. The books are ours.
Past Perfect Tenses
Past Perfect Tense mirip dengan Present Perfect Tense hanya saja beda di waktunya saja. PRESENT Perfect Tense mengenai suatu kejadian atau peristiwa yang SELESAI (sempurna, perfect) saat ini, contohnya: She has just gone (Dia baru saja pergi).
PAST Perfect Tense adalah bentuk lampau (Past) dari Present Perfect Tense itu, makanya disebut Past Perfect Tense.
Bedanya,,Kalau Present Perfect Tense menggunakan rumus S + Have/has + V3 maka Past Perfect Tense menggunakan bentuk lampau dari Has/has yaitu “HAD”.
Rumus Past Perfect Tense
Positif: S + had + V3
Negatif: S + had + not + V3
Tanya: Had + S + V3
Past Perfect Tense sering digunakan dengan menggunakan kalimat lain yang berbentuk lampau (Past Tense)
yang dihubungan dengan kata sambung seperti When (ketika), After
(setelah) untuk menekankan bahwa Perfectnya (Sudahnya) itu adalah di
masa lampau.
Contoh kejadiannya seperti ini:
“Kemarin Dia berangkat ke rumahku pagi-pagi bener, tetapi waktu ia sampai eh saya SUDAH pergi”. Tuh, lihatlah SUDAH perginya itu kan Perfect. Anda ingat pelajaran tentang Present Perfect Tense bahwa SUDAH itu adalah ciri-cirinya. Hanya saja SUDAH nya itu adalah kemarin (lampau). Itulah mengapa dalam kejadian ini kita menggunakan Past Perfect Tense.
Contoh kalimatnya:
-I had gone When He arrived at my home
“I had gone” adalah Past Perfect Tense, dengan subjectnya adalah I. Lihat ada “had” nya, dan kata kerja bentuk ketiganya (V3) adalah gone. Sesuai rumusnya S + had + V3. Kalimat pembandingnya adalah bentuk past tense: “When He arrived at my home”.
Contoh kalimat lainnya:
I had written 3 articles when you visited my blog for the first time.
Jadi Past Perfect Tense adalah tentang “Sudah, masa lalu”. Present Perfect Tense tentang “Sudah, kini”. Rumusnya mirip, karena sama-sama Perfect. Setiap Perfect pasti pakai kata kerja bentuk ke-3 baik itu pada Kata Kerja utamanya atau pada kata kerja bantu-nya.
Contoh kalimat lain dalam Past Perfect Tense:
-I had studied hard but I didn’t make good result in the exam.
-You had told me twice before I understood.
-Coba buat kalimat Anda paling tidak 3 biji, ayoo..
Past Perfect Tense Dalam Kalimat Negatif
Gampang saja, tinggal tambah NO setelah HAD. Contoh berikut telah disederhanakan:
-I had not studied hard, so I didn’t make good result
-You had not told me that, that’s why I didn’t understand
Perhatikan kalimat past tense di belakangnya sengaja saya ubah agar mengandung arti yang masuk akal saja. Jika tidak diganti kan menjadi aneh itu kalimat. Betul?
Past Perfect Tense Dalam Kalimat Tanya
Tinggal dibalik, Had nya di depan.
Rumusnya kan: Had + S + V3
-Had You studied hard bla bla bla?
-Had You told me …?
PAST Perfect Tense adalah bentuk lampau (Past) dari Present Perfect Tense itu, makanya disebut Past Perfect Tense.
Bedanya,,Kalau Present Perfect Tense menggunakan rumus S + Have/has + V3 maka Past Perfect Tense menggunakan bentuk lampau dari Has/has yaitu “HAD”.
Rumus Past Perfect Tense
Positif: S + had + V3
Negatif: S + had + not + V3
Tanya: Had + S + V3
Past Perfect Tense sering digunakan dengan menggunakan kalimat lain yang berbentuk lampau (Past Tense)
yang dihubungan dengan kata sambung seperti When (ketika), After
(setelah) untuk menekankan bahwa Perfectnya (Sudahnya) itu adalah di
masa lampau.
Contoh kejadiannya seperti ini:
“Kemarin Dia berangkat ke rumahku pagi-pagi bener, tetapi waktu ia sampai eh saya SUDAH pergi”. Tuh, lihatlah SUDAH perginya itu kan Perfect. Anda ingat pelajaran tentang Present Perfect Tense bahwa SUDAH itu adalah ciri-cirinya. Hanya saja SUDAH nya itu adalah kemarin (lampau). Itulah mengapa dalam kejadian ini kita menggunakan Past Perfect Tense.
Contoh kalimatnya:
-I had gone When He arrived at my home
“I had gone” adalah Past Perfect Tense, dengan subjectnya adalah I. Lihat ada “had” nya, dan kata kerja bentuk ketiganya (V3) adalah gone. Sesuai rumusnya S + had + V3. Kalimat pembandingnya adalah bentuk past tense: “When He arrived at my home”.
Contoh kalimat lainnya:
I had written 3 articles when you visited my blog for the first time.
Jadi Past Perfect Tense adalah tentang “Sudah, masa lalu”. Present Perfect Tense tentang “Sudah, kini”. Rumusnya mirip, karena sama-sama Perfect. Setiap Perfect pasti pakai kata kerja bentuk ke-3 baik itu pada Kata Kerja utamanya atau pada kata kerja bantu-nya.
Contoh kalimat lain dalam Past Perfect Tense:
-I had studied hard but I didn’t make good result in the exam.
-You had told me twice before I understood.
-Coba buat kalimat Anda paling tidak 3 biji, ayoo..
Past Perfect Tense Dalam Kalimat Negatif
Gampang saja, tinggal tambah NO setelah HAD. Contoh berikut telah disederhanakan:
-I had not studied hard, so I didn’t make good result
-You had not told me that, that’s why I didn’t understand
Perhatikan kalimat past tense di belakangnya sengaja saya ubah agar mengandung arti yang masuk akal saja. Jika tidak diganti kan menjadi aneh itu kalimat. Betul?
Past Perfect Tense Dalam Kalimat Tanya
Tinggal dibalik, Had nya di depan.
Rumusnya kan: Had + S + V3
-Had You studied hard bla bla bla?
-Had You told me …?
Rabu, 14 Oktober 2009
Present Perfect - Simple Past
Present Perfect
[has/have + past participle]
1. Present perfect - form
The present perfect of any verb is composed of two elements : the appropriate form of the auxiliary verb to have (present tense), plus the past participle of the main verb. The past participle of a regular verb is base+ed, e.g. played, arrived, looked. For irregular verbs, see the Table of irregular verbs in the section called 'Verbs'.
Affirmative
Subject
to have
past participle
She
has
visited
Negative
Subject
to have + not
past participle
She
hasn't
visited
Interrogative
to have
subject
past participle
Has
she
visited..?
Interrogative negative
to have + not subject past participle
Hasn't she visited...?
Example: to walk, present perfect
Affirmative
Negative
Interrogative
I have walked
I haven't walked
Have I walked?
You have walked
You haven't walked
Have you walked?
He, she, it has walked
He, she, it hasn't walked
Has he,she,it walked
We have walked
We haven't walked
Have we walked?
You have walked
You haven't walked
Have you walked?
They have walked
They haven't walked
Have they walked?
2. Present perfect, function
The Present Perfect is used to indicate a link between the present and the past. The time of the action is before now but not specified, and we are often more interested in the result than in the action itself.
BE CAREFUL! There may be a verb tense in your language with a similar form, but the meaning is probably NOT the same.
The present perfect is used to describe:
1.An action or situation that started in the past and continues in the present. Example: I have lived in Bristol since 1984 (= and I still do.)
2. An action performed during a period that has not yet finished. Example: She has been to the cinema twice this week (= and the week isn't over yet.)
3. A repeated action in an unspecified period between the past and now. Example: We have visited Portugal several times.
4. An action that was completed in the very recent past, (expressed by 'just'). Example: I have just finished my work.
5. An action when the time is not important. Example: He has read 'War and Peace'. (the result of his reading is important)
Note: When we want to give or ask details about when, where, who, we use the simple past. Example: He read 'War and Peace' last week.
Examples:
1. Actions started in the past and continuing in the present.
a. They haven't lived here for years.
b. She has worked in the bank for five years.
c. We have had the same car for ten years.
d. Have you played the piano since you were a child?
2. When the time period referred to has not finished.
a. I have worked hard this week.
b. It has rained a lot this year.
c. We haven't seen her today.
3. Actions repeated in an unspecified period between the past and now.
a. They have seen that film six times.
b. It has happened several times already.
c. She has visited them frequently.
d. We have eaten at that restaurant many times.
4. Actions completed in the very recent past (+just).
a. Have you just finished work?
b. I have just eaten.
c. We have just seen her.
d. Has he just left?
5. When the precise time of the action is not important or not known.
a. Someone has eaten my soup!
b. Have you seen 'Gone with the Wind'?
c. She's studied Japanese, Russian and English.
SIMPLE PAST
BE CAREFUL! The simple past in English may look like a tense in your own language, but the meaning may be different.
1. Simple past, form
Regular verbs: base+ed
e.g. walked, showed, watched, played, smiled, stopped
Irregular verbs: see list in verbs
Simple past, be, have, do:
Subject
Verb
Be
Have
Do
I
was
had
did
You
were
had
did
He, she, it
was
had
did
We
were
had
did
You
were
had
did
They
were
had
did
Affirmative
a. I was in Japan last year
b. She had a headache yesterday.
c. We did our homework last night.
Negative and interrogative
Note: For the negative and interrogative simple past form of "do" as an ordinary verb, use the auxiliary "do", e.g. We didn't do our homework last night. The negative of "have" in the simple past is usually formed using the auxiliary "do", but sometimes by simply adding not or the contraction "n't".
The interrogative form of "have" in the simple past normally uses the auxiliary "do".
* They weren't in Rio last summer.
* We hadn't any money.
* We didn't have time to visit the Eiffel Tower.
* We didn't do our exercises this morning.
* Were they in Iceland last January?
* Did you have a bicycle when you were a boy?
* Did you do much climbing in Switzerland?
Simple past, regular verbs
Affirmative
Subject
verb + ed
I
washed
Negative
Subject
did not
infinitive without to
They
didn't
visit ...
Interrogative
Did
subject
infinitive without to
Did
she
arrive...?
Interrogative negative
Did not
subject
infinitive without to
Didn't
you
like..?
Example: to walk, simple past.
Affirmative
Negative
Interrogative
I walked
I didn't walk
Did I walk?
You walked
You didn't walk
Did you walk?
He,she,it walked
He didn't walk
Did he walk?
We walked
We didn't walk
Did we walk?
You walked
You didn't walk
Did you walk?
They walked
They didn't walk
Did they walk?
Note: For the negative and interrogative form of all verbs in the simple past, always use the auxiliary 'did''.
Examples: Simple past, irregular verbs
to go
a. He went to a club last night.
b. Did he go to the cinema last night?
c. He didn't go to bed early last night.
to give
d. We gave her a doll for her birthday.
e. They didn't give John their new address.
f. Did Barry give you my passport?
to come
g. My parents came to visit me last July.
h. We didn't come because it was raining.
i. Did he come to your party last week?
2. Simple past, function
The simple past is used to talk about a completed action in a time before now. Duration is not important. The time of the action can be in the recent past or the distant past.
* John Cabot sailed to America in 1498.
* My father died last year.
* He lived in Fiji in 1976.
* We crossed the Channel yesterday.
You always use the simple past when you say when something happened, so it is associated with certain past time expressions
Examples:
* frequency:
often, sometimes, always;
* a definite point in time:
last week, when I was a child, yesterday, six weeks ago.
* an indefinite point in time:
the other day, ages ago, a long time ago etc.
Note: the word ago is a useful way of expressing the distance into the past. It is placed after the period of time e.g. a week ago, three years ago, a minute ago.
Examples:
a. Yesterday, I arrived in Geneva.
b. She finished her work at seven o'clock.
c. We saw a good film last week.
d. I went to the theatre last night.
e. She played the piano when she was a child.
f. He sent me a letter six months ago.
g. Peter left five minutes ago.
[has/have + past participle]
1. Present perfect - form
The present perfect of any verb is composed of two elements : the appropriate form of the auxiliary verb to have (present tense), plus the past participle of the main verb. The past participle of a regular verb is base+ed, e.g. played, arrived, looked. For irregular verbs, see the Table of irregular verbs in the section called 'Verbs'.
Affirmative
Subject
to have
past participle
She
has
visited
Negative
Subject
to have + not
past participle
She
hasn't
visited
Interrogative
to have
subject
past participle
Has
she
visited..?
Interrogative negative
to have + not subject past participle
Hasn't she visited...?
Example: to walk, present perfect
Affirmative
Negative
Interrogative
I have walked
I haven't walked
Have I walked?
You have walked
You haven't walked
Have you walked?
He, she, it has walked
He, she, it hasn't walked
Has he,she,it walked
We have walked
We haven't walked
Have we walked?
You have walked
You haven't walked
Have you walked?
They have walked
They haven't walked
Have they walked?
2. Present perfect, function
The Present Perfect is used to indicate a link between the present and the past. The time of the action is before now but not specified, and we are often more interested in the result than in the action itself.
BE CAREFUL! There may be a verb tense in your language with a similar form, but the meaning is probably NOT the same.
The present perfect is used to describe:
1.An action or situation that started in the past and continues in the present. Example: I have lived in Bristol since 1984 (= and I still do.)
2. An action performed during a period that has not yet finished. Example: She has been to the cinema twice this week (= and the week isn't over yet.)
3. A repeated action in an unspecified period between the past and now. Example: We have visited Portugal several times.
4. An action that was completed in the very recent past, (expressed by 'just'). Example: I have just finished my work.
5. An action when the time is not important. Example: He has read 'War and Peace'. (the result of his reading is important)
Note: When we want to give or ask details about when, where, who, we use the simple past. Example: He read 'War and Peace' last week.
Examples:
1. Actions started in the past and continuing in the present.
a. They haven't lived here for years.
b. She has worked in the bank for five years.
c. We have had the same car for ten years.
d. Have you played the piano since you were a child?
2. When the time period referred to has not finished.
a. I have worked hard this week.
b. It has rained a lot this year.
c. We haven't seen her today.
3. Actions repeated in an unspecified period between the past and now.
a. They have seen that film six times.
b. It has happened several times already.
c. She has visited them frequently.
d. We have eaten at that restaurant many times.
4. Actions completed in the very recent past (+just).
a. Have you just finished work?
b. I have just eaten.
c. We have just seen her.
d. Has he just left?
5. When the precise time of the action is not important or not known.
a. Someone has eaten my soup!
b. Have you seen 'Gone with the Wind'?
c. She's studied Japanese, Russian and English.
SIMPLE PAST
BE CAREFUL! The simple past in English may look like a tense in your own language, but the meaning may be different.
1. Simple past, form
Regular verbs: base+ed
e.g. walked, showed, watched, played, smiled, stopped
Irregular verbs: see list in verbs
Simple past, be, have, do:
Subject
Verb
Be
Have
Do
I
was
had
did
You
were
had
did
He, she, it
was
had
did
We
were
had
did
You
were
had
did
They
were
had
did
Affirmative
a. I was in Japan last year
b. She had a headache yesterday.
c. We did our homework last night.
Negative and interrogative
Note: For the negative and interrogative simple past form of "do" as an ordinary verb, use the auxiliary "do", e.g. We didn't do our homework last night. The negative of "have" in the simple past is usually formed using the auxiliary "do", but sometimes by simply adding not or the contraction "n't".
The interrogative form of "have" in the simple past normally uses the auxiliary "do".
* They weren't in Rio last summer.
* We hadn't any money.
* We didn't have time to visit the Eiffel Tower.
* We didn't do our exercises this morning.
* Were they in Iceland last January?
* Did you have a bicycle when you were a boy?
* Did you do much climbing in Switzerland?
Simple past, regular verbs
Affirmative
Subject
verb + ed
I
washed
Negative
Subject
did not
infinitive without to
They
didn't
visit ...
Interrogative
Did
subject
infinitive without to
Did
she
arrive...?
Interrogative negative
Did not
subject
infinitive without to
Didn't
you
like..?
Example: to walk, simple past.
Affirmative
Negative
Interrogative
I walked
I didn't walk
Did I walk?
You walked
You didn't walk
Did you walk?
He,she,it walked
He didn't walk
Did he walk?
We walked
We didn't walk
Did we walk?
You walked
You didn't walk
Did you walk?
They walked
They didn't walk
Did they walk?
Note: For the negative and interrogative form of all verbs in the simple past, always use the auxiliary 'did''.
Examples: Simple past, irregular verbs
to go
a. He went to a club last night.
b. Did he go to the cinema last night?
c. He didn't go to bed early last night.
to give
d. We gave her a doll for her birthday.
e. They didn't give John their new address.
f. Did Barry give you my passport?
to come
g. My parents came to visit me last July.
h. We didn't come because it was raining.
i. Did he come to your party last week?
2. Simple past, function
The simple past is used to talk about a completed action in a time before now. Duration is not important. The time of the action can be in the recent past or the distant past.
* John Cabot sailed to America in 1498.
* My father died last year.
* He lived in Fiji in 1976.
* We crossed the Channel yesterday.
You always use the simple past when you say when something happened, so it is associated with certain past time expressions
Examples:
* frequency:
often, sometimes, always;
* a definite point in time:
last week, when I was a child, yesterday, six weeks ago.
* an indefinite point in time:
the other day, ages ago, a long time ago etc.
Note: the word ago is a useful way of expressing the distance into the past. It is placed after the period of time e.g. a week ago, three years ago, a minute ago.
Examples:
a. Yesterday, I arrived in Geneva.
b. She finished her work at seven o'clock.
c. We saw a good film last week.
d. I went to the theatre last night.
e. She played the piano when she was a child.
f. He sent me a letter six months ago.
g. Peter left five minutes ago.
Simple Present – Present Progressive
Present Progressive
Notes:
1. The written lesson is below.
2. Links to quizzes, tests, etc. are to the left.
The present progressive is formed by combining the verb "to be" with the present participle. (The present participle is merely the "-ing" form of a verb.)
I am studying.
I am studying with María.
In English, present progressive can be used to describe what is happening now, or what will happen in the future.
I am studying now.
I am studying with María tonight.
In Spanish, the present progressive is only used to describe an action that is in the process of taking place. It is not used for future actions.
I am studying now.
(use present progressive)
I am studying with María tonight.
(do not use present progressive)
To form the present progressive in Spanish, combine a form of "estar" with the present participle.
Estoy hablando.
I am speaking.
Juan está comiendo.
John is eating.
María está escribiendo una carta.
Mary is writing a letter.
In order to form the present progressive, you must know how to conjugate the verb estar, and how to form the present participle. You already know how to conjugate the verb estar:
estar
estoy
estás
está
estamos
estáis
están
To form the present participle of regular -ar verbs, add -ando to the stem of the verb.
hablar: hablando
(hablar - ar + ando)
trabajar: trabajando
(trabajar - ar + ando)
estudiar: estudiando
(estudiar - ar + ando)
To form the present participle of regular -er and -ir verbs, add -iendo to the stem of the verb.
comer: comiendo
(comer - er + iendo)
hacer: haciendo
(hacer - er + iendo)
vivir: viviendo
(vivir - ir + iendo)
escribir: escribiendo
(escribir - ir + iendo)
To form the present participle of -ir stem changing verbs, change e:i and o:u in the stem, and then add -iendo to the stem of the verb.
servir: sirviendo
pedir: pidiendo
decir: diciendo
dormir: durmiendo
morir: muriendo
poder: pudiendo
Sometimes when forming the present participle it is necessary to change the spelling of a word so that it agrees with the way it is pronounced. We call this an "orthographic" change. Here are some common examples:
caer: cayendo
creer: creyendo
huir: huyendo
ir: yendo
influir: influyendo
oír: oyendo
traer: trayendo
leer: leyendo
seguir: siguiendo
The following examples illustrate the rules for forming the present participle.
hablar: hablando (-ar)
comer: comiendo (-er)
vivir: viviendo (-ir)
decir: diciendo (e:i)
dormir: durmiendo (o:u)
leer: leyendo (orthographic)
seguir: siguiendo (orthographic)
To form the present progressive, simply conjugate the verb estar to agree with the subject of the sentence, and follow it with the present participle.
Juan está comiendo pan.
John is eating bread.
María y Carmen están hablando con nosotros.
Mary and Carmen are speaking with us.
Remember, only use the present progressive for actions that are "in progress." Compare the uses of the present indicative with the uses of the present progressive.
Estudio español. (Present Indicative)
I study Spanish.
I am studying Spanish (these days).
I do study Spanish.
Estoy estudiando español. (Present Progressive)
I am studying (right now, at this moment) Spanish.
It is important to remember that you would never use the present progressive to say something like "We are going to Spain this summer." Use present progressive only for actions that are "in progress."
Let's add two more verb flashcards: one for present progressive and one for practice in forming the present participle:
Verb Flashcards
Complete List
Present Progressive
estar + present participle
I am speaking (right now, at this moment)
Never use present progressive for something that will occur in the future.
Present Participle (-ando, -iendo, yendo)
hablar - hablando (-ar)
comer - comiendo (-er)
vivir - viviendo (-ir)
decir - diciendo (e:i)
dormir - durmiendo (o:u)
leer - leyendo (orthographic)
seguir: siguiendo (orthographic)
Simple Present
Ada beberapa penggunaan dari simple present tense, yaitu :
untuk menyatakan kegiatan yang berulang untuk menyatakan generalisasi atau kegiatan yang biasa berlangsung. Untuk menyetakan kegiatan saat ini. Untuk lebih jelasnya perhatikan penjelesan di bawah ini
1. Repeated Actions (Kegiatan berulang)
Simple present dapat digunakan untuk menyatakan gagasan atau kegiatan yang dilakukan sering dilakukan berulangkali seperti bangun tidur, atau kebiasaan seperti berolahraga, jadwal pemberangkatan kendaraan dan lain sebagainya, kegiatan tersebut dapat berupa kebiasaan, hobby, kegiatan sehari-hari, jadwal, dan juga kebiasaan yang selalu tidak dilakukan.
Dari gambar diatas tanda silang warna biru adalah kejadian yang dilakukan, jadi kejadian tersebut selain dilakukan saat ini (persent) juga dilakukan pada waktu lampau (past) dan yang akan datang (future)
EXAMPLES:
* I play tennis.
* She does not play tennis.
* The train leaves every morning at 8 am.
* The train does not leave at 9am.
* She always forgets her purse.
* He never forgets his wallet.
* Every twelve months, the Earth circles the sun.
* The sun does not circle the Earth.
2. Menyatakan Kebenaran atau keadaan yang umum (Facts or Generalizations)
Simple Present dapat juga digunakan untuk mengekspresikan suatu kejadian yang benar pada masa lampau, sekarang maupun yang akan datang, misalnya matahari terbit dari barat, satu jam 360 menit dan lain sebagainya. Selain itu Simple Present juga digunakan untuk menyatakan generalisasi (keadaan yang umum) terhadap pikiran orang, misalnya orang batak suka musik, burung mempunyai sayap dan lain sebagainya
Perhatikan gambar berikut untuk lebih jelasnya
.
EXAMPLES:
* Cats like milk.
* Birds do not like milk.
* Jakarta is in Indonesia
* Surabaya is not in the United Kingdom.
* Windows are made of glass.
* Windows are not made of wood.
* Jakarta is a small city. (It is not important that this fact is untrue.)
3. Keadaan Sekarang Now (Non-Continuous Verbs)
Simple Present digunakan juga untuk menyatakan kegiatan yang berlangsung maupun tidak berlangsung saat ini secasra spontan. Namun hanya bisa digunakan dengan Non-continuous Verbs dan Mixed Verbs.
EXAMPLES:
* I am here now.
* She is not here now.
* He needs help right now.
* He does not need help now.
* He has a car.
Diterjemahkan dari : englishpage.com
PRESENT artinya adalah kini, sekarang.
Rumusnya:
Positif: S + V1 (s/es)
Negatif: S + DO/DOES + NOT + V1
Tanya: DO/DOES + S + V1
Contoh Kalimat Positif:
* I drink coffee
* She drinks coffe
* We drink coffee
Ya, sengaja pelajaran Tense bahasa inggris ini dibuat simple saja agar cepat faham. Anda perlu mengembangkannya sendiri misalnya dengan membuat 100 contoh sendiri. Pasti Anda perlu kamus juga, karena belajar tenses lalu mentok dengan suatu kata kerja maka biasanya tidak jadi, hehe..
Cara Membaca Rumus:
S artinya Subject, V1 artinya Verb1 atau kata kerja bentuk pertama. Garis miring artinya ya Atau dong!.
Kapan pakai S atau ES dan kapan tidak?
Kalau Subjectnya He, She, It, John, Mufli, Ellen atau Orang ketiga TUNGGAL maka kata kerjanya tambah S atau ES. Tidak sembarang tambah S atau ES juga nih, ada daftarnya. Daftarnya itu bayak sekali.
Di atas tadi ada istilah Orang Ketiga Tunggal, maksudnya gini: Orang ketiga adalah orang yang kita bicarakan, yang kita omongin. Sedangkan orang pertama ya yang bicara. Orang kedua lawan bicara. Tunggal ya satu. Jadi orang ketiga tunggal adalah orang yang kita bicarakan dan satu saja dia itu. Misalnya kita berdua ngomongin John Scoping. Yang ngomong saya, yang dengar Anda, yang dibicarakan John Scoping (orang ketiga tunggal).
John Scoping belajar Tenses.
John Scoping learnS english.
Tidak bisa LearnES, mengapa? ya memang begitu!. Tetapi yang ini malah tambah ES:
John Scoping goES to School (tambah ES).
Kalimat Negatif Present Tense
Bentuk Negatif, artinya menyatakan TIDAK. Maka sesuai rumus Present Tense, setelah SUBJECT ditambah DO atau DOES, baru NOT, lalu tambah kata kerja bentuk pertama tanpa S atau ES lagi. S atau ES nya dimana? Sudah di doES tadi.
Untuk I, WE, YOU, THEY tambah DO
Untuk SHE, HE, IT, Mufli, Ellen tambah DOES
I do not drink coffee.
She does not drink coffee.
John Scoping does not learn english.
Coba perhatikan She does not drink coffee. Drink nya tidak pake S lagi, pindah ke doES. Biasakan saja, Present Simple Tense ini sepertinya rumit tetapi kalau faham maka enak banget. Ulangi saja baca dari atas 10 kali lagi, biar meresap benar, hehe.. Bikin juga 10 contoh Anda sendiri dengan kata kerja yang berbeda. Yes, belajar bahasa Inggris tak boleh manja, harus aktif, baru akan bisa.
Kalimat Tanya Present Tense
Kalimat tanya untuk Present Tense sesuai rumus diatas, atau saya tulis lagi seperti ini:
Tanya: DO/DOES + S + V1
Sama saja pasangannya. Untuk I, WE, YOU, THEY gunakan DO. Untuk SHE, HE, IT, Mufli, Ellen gunakan DOES. Contohnya begini:
Kalimat positifnya: I drink coffee
Kalimat tanya menjadi: DO you drink cofee?
Kalimat positif: She drinks coffe
Kalimat tanya: DOES She drink coffee?
Kalimat tanya seperti diatas disebut juga YES/NO Question. Karena jawabannya memang Yes atau No. Do You drink coffee? “Yes I do” jawabnya. Atau bisa bisa dijawab dengan lengkap: “Yes, I do drink coffee”. Dihilangkan DO nya juga boleh, menjadi kalimat positif lagi: “Yes I drink coffee”.
Ya, memang benar kalau Present Tense ini lebih rumit dibandingkan dengan Present Continuous Tense karena tiba-tiba kok pake DO, eh untuk orang ketiga tunggal pakai DOES segala, hehe.. Kalau dalam Present Continuous Tense nanti tinggal dibalik doang.
Notes:
1. The written lesson is below.
2. Links to quizzes, tests, etc. are to the left.
The present progressive is formed by combining the verb "to be" with the present participle. (The present participle is merely the "-ing" form of a verb.)
I am studying.
I am studying with María.
In English, present progressive can be used to describe what is happening now, or what will happen in the future.
I am studying now.
I am studying with María tonight.
In Spanish, the present progressive is only used to describe an action that is in the process of taking place. It is not used for future actions.
I am studying now.
(use present progressive)
I am studying with María tonight.
(do not use present progressive)
To form the present progressive in Spanish, combine a form of "estar" with the present participle.
Estoy hablando.
I am speaking.
Juan está comiendo.
John is eating.
María está escribiendo una carta.
Mary is writing a letter.
In order to form the present progressive, you must know how to conjugate the verb estar, and how to form the present participle. You already know how to conjugate the verb estar:
estar
estoy
estás
está
estamos
estáis
están
To form the present participle of regular -ar verbs, add -ando to the stem of the verb.
hablar: hablando
(hablar - ar + ando)
trabajar: trabajando
(trabajar - ar + ando)
estudiar: estudiando
(estudiar - ar + ando)
To form the present participle of regular -er and -ir verbs, add -iendo to the stem of the verb.
comer: comiendo
(comer - er + iendo)
hacer: haciendo
(hacer - er + iendo)
vivir: viviendo
(vivir - ir + iendo)
escribir: escribiendo
(escribir - ir + iendo)
To form the present participle of -ir stem changing verbs, change e:i and o:u in the stem, and then add -iendo to the stem of the verb.
servir: sirviendo
pedir: pidiendo
decir: diciendo
dormir: durmiendo
morir: muriendo
poder: pudiendo
Sometimes when forming the present participle it is necessary to change the spelling of a word so that it agrees with the way it is pronounced. We call this an "orthographic" change. Here are some common examples:
caer: cayendo
creer: creyendo
huir: huyendo
ir: yendo
influir: influyendo
oír: oyendo
traer: trayendo
leer: leyendo
seguir: siguiendo
The following examples illustrate the rules for forming the present participle.
hablar: hablando (-ar)
comer: comiendo (-er)
vivir: viviendo (-ir)
decir: diciendo (e:i)
dormir: durmiendo (o:u)
leer: leyendo (orthographic)
seguir: siguiendo (orthographic)
To form the present progressive, simply conjugate the verb estar to agree with the subject of the sentence, and follow it with the present participle.
Juan está comiendo pan.
John is eating bread.
María y Carmen están hablando con nosotros.
Mary and Carmen are speaking with us.
Remember, only use the present progressive for actions that are "in progress." Compare the uses of the present indicative with the uses of the present progressive.
Estudio español. (Present Indicative)
I study Spanish.
I am studying Spanish (these days).
I do study Spanish.
Estoy estudiando español. (Present Progressive)
I am studying (right now, at this moment) Spanish.
It is important to remember that you would never use the present progressive to say something like "We are going to Spain this summer." Use present progressive only for actions that are "in progress."
Let's add two more verb flashcards: one for present progressive and one for practice in forming the present participle:
Verb Flashcards
Complete List
Present Progressive
estar + present participle
I am speaking (right now, at this moment)
Never use present progressive for something that will occur in the future.
Present Participle (-ando, -iendo, yendo)
hablar - hablando (-ar)
comer - comiendo (-er)
vivir - viviendo (-ir)
decir - diciendo (e:i)
dormir - durmiendo (o:u)
leer - leyendo (orthographic)
seguir: siguiendo (orthographic)
Simple Present
Ada beberapa penggunaan dari simple present tense, yaitu :
untuk menyatakan kegiatan yang berulang untuk menyatakan generalisasi atau kegiatan yang biasa berlangsung. Untuk menyetakan kegiatan saat ini. Untuk lebih jelasnya perhatikan penjelesan di bawah ini
1. Repeated Actions (Kegiatan berulang)
Simple present dapat digunakan untuk menyatakan gagasan atau kegiatan yang dilakukan sering dilakukan berulangkali seperti bangun tidur, atau kebiasaan seperti berolahraga, jadwal pemberangkatan kendaraan dan lain sebagainya, kegiatan tersebut dapat berupa kebiasaan, hobby, kegiatan sehari-hari, jadwal, dan juga kebiasaan yang selalu tidak dilakukan.
Dari gambar diatas tanda silang warna biru adalah kejadian yang dilakukan, jadi kejadian tersebut selain dilakukan saat ini (persent) juga dilakukan pada waktu lampau (past) dan yang akan datang (future)
EXAMPLES:
* I play tennis.
* She does not play tennis.
* The train leaves every morning at 8 am.
* The train does not leave at 9am.
* She always forgets her purse.
* He never forgets his wallet.
* Every twelve months, the Earth circles the sun.
* The sun does not circle the Earth.
2. Menyatakan Kebenaran atau keadaan yang umum (Facts or Generalizations)
Simple Present dapat juga digunakan untuk mengekspresikan suatu kejadian yang benar pada masa lampau, sekarang maupun yang akan datang, misalnya matahari terbit dari barat, satu jam 360 menit dan lain sebagainya. Selain itu Simple Present juga digunakan untuk menyatakan generalisasi (keadaan yang umum) terhadap pikiran orang, misalnya orang batak suka musik, burung mempunyai sayap dan lain sebagainya
Perhatikan gambar berikut untuk lebih jelasnya
.
EXAMPLES:
* Cats like milk.
* Birds do not like milk.
* Jakarta is in Indonesia
* Surabaya is not in the United Kingdom.
* Windows are made of glass.
* Windows are not made of wood.
* Jakarta is a small city. (It is not important that this fact is untrue.)
3. Keadaan Sekarang Now (Non-Continuous Verbs)
Simple Present digunakan juga untuk menyatakan kegiatan yang berlangsung maupun tidak berlangsung saat ini secasra spontan. Namun hanya bisa digunakan dengan Non-continuous Verbs dan Mixed Verbs.
EXAMPLES:
* I am here now.
* She is not here now.
* He needs help right now.
* He does not need help now.
* He has a car.
Diterjemahkan dari : englishpage.com
PRESENT artinya adalah kini, sekarang.
Rumusnya:
Positif: S + V1 (s/es)
Negatif: S + DO/DOES + NOT + V1
Tanya: DO/DOES + S + V1
Contoh Kalimat Positif:
* I drink coffee
* She drinks coffe
* We drink coffee
Ya, sengaja pelajaran Tense bahasa inggris ini dibuat simple saja agar cepat faham. Anda perlu mengembangkannya sendiri misalnya dengan membuat 100 contoh sendiri. Pasti Anda perlu kamus juga, karena belajar tenses lalu mentok dengan suatu kata kerja maka biasanya tidak jadi, hehe..
Cara Membaca Rumus:
S artinya Subject, V1 artinya Verb1 atau kata kerja bentuk pertama. Garis miring artinya ya Atau dong!.
Kapan pakai S atau ES dan kapan tidak?
Kalau Subjectnya He, She, It, John, Mufli, Ellen atau Orang ketiga TUNGGAL maka kata kerjanya tambah S atau ES. Tidak sembarang tambah S atau ES juga nih, ada daftarnya. Daftarnya itu bayak sekali.
Di atas tadi ada istilah Orang Ketiga Tunggal, maksudnya gini: Orang ketiga adalah orang yang kita bicarakan, yang kita omongin. Sedangkan orang pertama ya yang bicara. Orang kedua lawan bicara. Tunggal ya satu. Jadi orang ketiga tunggal adalah orang yang kita bicarakan dan satu saja dia itu. Misalnya kita berdua ngomongin John Scoping. Yang ngomong saya, yang dengar Anda, yang dibicarakan John Scoping (orang ketiga tunggal).
John Scoping belajar Tenses.
John Scoping learnS english.
Tidak bisa LearnES, mengapa? ya memang begitu!. Tetapi yang ini malah tambah ES:
John Scoping goES to School (tambah ES).
Kalimat Negatif Present Tense
Bentuk Negatif, artinya menyatakan TIDAK. Maka sesuai rumus Present Tense, setelah SUBJECT ditambah DO atau DOES, baru NOT, lalu tambah kata kerja bentuk pertama tanpa S atau ES lagi. S atau ES nya dimana? Sudah di doES tadi.
Untuk I, WE, YOU, THEY tambah DO
Untuk SHE, HE, IT, Mufli, Ellen tambah DOES
I do not drink coffee.
She does not drink coffee.
John Scoping does not learn english.
Coba perhatikan She does not drink coffee. Drink nya tidak pake S lagi, pindah ke doES. Biasakan saja, Present Simple Tense ini sepertinya rumit tetapi kalau faham maka enak banget. Ulangi saja baca dari atas 10 kali lagi, biar meresap benar, hehe.. Bikin juga 10 contoh Anda sendiri dengan kata kerja yang berbeda. Yes, belajar bahasa Inggris tak boleh manja, harus aktif, baru akan bisa.
Kalimat Tanya Present Tense
Kalimat tanya untuk Present Tense sesuai rumus diatas, atau saya tulis lagi seperti ini:
Tanya: DO/DOES + S + V1
Sama saja pasangannya. Untuk I, WE, YOU, THEY gunakan DO. Untuk SHE, HE, IT, Mufli, Ellen gunakan DOES. Contohnya begini:
Kalimat positifnya: I drink coffee
Kalimat tanya menjadi: DO you drink cofee?
Kalimat positif: She drinks coffe
Kalimat tanya: DOES She drink coffee?
Kalimat tanya seperti diatas disebut juga YES/NO Question. Karena jawabannya memang Yes atau No. Do You drink coffee? “Yes I do” jawabnya. Atau bisa bisa dijawab dengan lengkap: “Yes, I do drink coffee”. Dihilangkan DO nya juga boleh, menjadi kalimat positif lagi: “Yes I drink coffee”.
Ya, memang benar kalau Present Tense ini lebih rumit dibandingkan dengan Present Continuous Tense karena tiba-tiba kok pake DO, eh untuk orang ketiga tunggal pakai DOES segala, hehe.. Kalau dalam Present Continuous Tense nanti tinggal dibalik doang.
OTHERS, THE OTHERS, & ANOTHERS
Kata other, another, dan others dapat diartikan dengan : yang lain atau lainnya. Ketiga kata tersebut sangat mudah membingungkan. Maka untuk menentukan bagaimana menggunakannya dengan tepat masing-masing kata itu harus diperhatikan empat hal.
1. Jika kata itu singular (tunggal) atau plural (jamak).
2. Jika kata itu definite –the- (tentu) atau indefinite –a- (tak tentu)
3. Jika kata itu berfungsi sebagai adjective yang menerangkan noun atau senantiasa bersama dengan noun.
4. Jika kata itu berfungsi sebagai pronoun yang dapat berdiri sendiri.
Perhatikanlah contoh-contoh berikut :
a. I have another (adj.) book
b. I have another (pron.)
“Perhatikan bahwa another digunakan hanya untuk menunjuk kepada an indefinite (tak tentu). Dan dengan benda tunggal (singular)”
c. I have other (adj.) books.
d. I have others. (pron)
e. I have the other book (adj.)
f. I have the other (pron.)
g. I have the other books (adj.)
h. I have the others (pron).
“Perhatikan bahwa Others hanya digunakan sebagai plural pronoun yang tidak bersama dengan noun(dapat berdiri sendiri). Sedangkan other dapat digunakan untuk semuanya”
i. I have three books, two are mine. The other book is yours. (The others is yours).
j. I have three books, one is mine. The others are yours. (The others are yours).
k. If you are still thirsty, I’ll make another pot of coffee.
Example :
OTHER -- the singular form. The word refers to something that is different from something else. For instance, Director A makes a movie based on a famous novel. Director B makes a different movie based on the same novel.
Luke: "Did you like Director A's movie?"
Ted: "Yes, but I liked the OTHER version much better."
Luke: "What do you think of my new wrist watch?" [On his right wrist.]
Ted: "I think you should wear it on your OTHER wrist."
Two senators write two different pieces of legislation about the same topic. "I like Senator Luke's legislation, but the OTHER one will probably be approved."
So, when we use the singular word "other," we are actually referring to something different from something else: X is fine, but I think the OTHER ["Y"] is more acceptable.
*****
OTHERS -- the plural form, for more than one "other"
Some essays are easy to read; OTHERS are much more difficult.
Many people chose to vote in the election. OTHERS simply stayed at home, not interested in voting at all. [OTHERS clearly indicates the "different" or "non-voting" people.]
*****
THE OTHERS -- same as above, but used in cases where the article "the" is necessary.
Luke: "Would you like to have THESE shirts?"
Ted: "No, I think THE OTHERS look more presentable."
The "chosen" people lived in the wealthy homes; all THE OTHERS lived in very poor houses. ["The others" in this example means "the people who are NOT wealthy" or THE OTHERS.]
*****
ANOTHER -- The dictionary definition is this: "different or distinct from the one first considered" OR "additional" OR "later."
Different or distinct --
Luke: "Are you going to write your essay about global warming?"
Ted: "I had thought I would, but I have changed my mind and will write on ANOTHER topic."
Additional --
Luke: "Did you get enough to eat?"
Ted: "No, I think I'll have another piece of pie."
Later --
Luke: "Are you taking a trip this weekend?"
Ted: "I think I'll wait until ANOTHER time."
Kata other, another, dan others dapat diartikan dengan : yang lain atau lainnya. Ketiga kata tersebut sangat mudah membingungkan. Maka untuk menentukan bagaimana menggunakannya dengan tepat masing-masing kata itu harus diperhatikan empat hal.
1. Jika kata itu singular (tunggal) atau plural (jamak).
2. Jika kata itu definite –the- (tentu) atau indefinite –a- (tak tentu)
3. Jika kata itu berfungsi sebagai adjective yang menerangkan noun atau senantiasa bersama dengan noun.
4. Jika kata itu berfungsi sebagai pronoun yang dapat berdiri sendiri.
Perhatikanlah contoh-contoh berikut :
a. I have another (adj.) book
b. I have another (pron.)
“Perhatikan bahwa another digunakan hanya untuk menunjuk kepada an indefinite (tak tentu). Dan dengan benda tunggal (singular)”
c. I have other (adj.) books.
d. I have others. (pron)
e. I have the other book (adj.)
f. I have the other (pron.)
g. I have the other books (adj.)
h. I have the others (pron).
“Perhatikan bahwa Others hanya digunakan sebagai plural pronoun yang tidak bersama dengan noun(dapat berdiri sendiri). Sedangkan other dapat digunakan untuk semuanya”
i. I have three books, two are mine. The other book is yours. (The others is yours).
j. I have three books, one is mine. The others are yours. (The others are yours).
k. If you are still thirsty, I’ll make another pot of coffee.
Example :
OTHER -- the singular form. The word refers to something that is different from something else. For instance, Director A makes a movie based on a famous novel. Director B makes a different movie based on the same novel.
Luke: "Did you like Director A's movie?"
Ted: "Yes, but I liked the OTHER version much better."
Luke: "What do you think of my new wrist watch?" [On his right wrist.]
Ted: "I think you should wear it on your OTHER wrist."
Two senators write two different pieces of legislation about the same topic. "I like Senator Luke's legislation, but the OTHER one will probably be approved."
So, when we use the singular word "other," we are actually referring to something different from something else: X is fine, but I think the OTHER ["Y"] is more acceptable.
*****
OTHERS -- the plural form, for more than one "other"
Some essays are easy to read; OTHERS are much more difficult.
Many people chose to vote in the election. OTHERS simply stayed at home, not interested in voting at all. [OTHERS clearly indicates the "different" or "non-voting" people.]
*****
THE OTHERS -- same as above, but used in cases where the article "the" is necessary.
Luke: "Would you like to have THESE shirts?"
Ted: "No, I think THE OTHERS look more presentable."
The "chosen" people lived in the wealthy homes; all THE OTHERS lived in very poor houses. ["The others" in this example means "the people who are NOT wealthy" or THE OTHERS.]
*****
ANOTHER -- The dictionary definition is this: "different or distinct from the one first considered" OR "additional" OR "later."
Different or distinct --
Luke: "Are you going to write your essay about global warming?"
Ted: "I had thought I would, but I have changed my mind and will write on ANOTHER topic."
Additional --
Luke: "Did you get enough to eat?"
Ted: "No, I think I'll have another piece of pie."
Later --
Luke: "Are you taking a trip this weekend?"
Ted: "I think I'll wait until ANOTHER time."
Articles, Determiners,
and Quantifiers
Definition
Articles, determiners, and quantifiers are those little words that precede and modify nouns:
the teacher, a college, a bit of honey, that person, those people, whatever purpose, either way, your choice
Sometimes these words will tell the reader or listener whether we're referring to a specific or general thing (the garage out back; A horse! A horse! My kingdom for a horse!); sometimes they tell how much or how many (lots of trees, several books, a great deal of confusion). The choice of the proper article or determiner to precede a noun or noun phrase is usually not a problem for writers who have grown up speaking English, nor is it a serious problem for non-native writers whose first language is a romance language such as Spanish. For other writers, though, this can be a considerable obstacle on the way to their mastery of English. In fact, some students from eastern European countries — where their native language has either no articles or an altogether different system of choosing articles and determiners — find that these "little words" can create problems long after every other aspect of English has been mastered.
Determiners are said to "mark" nouns. That is to say, you know a determiner will be followed by a noun. Some categories of determiners are limited (there are only three articles, a handful of possessive pronouns, etc.), but the possessive nouns are as limitless as nouns themselves. This limited nature of most determiner categories, however, explains why determiners are grouped apart from adjectives even though both serve a modifying function. We can imagine that the language will never tire of inventing new adjectives; the determiners (except for those possessive nouns), on the other hand, are well established, and this class of words is not going to grow in number. These categories of determiners are as follows: the articles (an, a, the — see below; possessive nouns (Joe's, the priest's, my mother's); possessive pronouns, (his, your, their, whose, etc.); numbers (one, two, etc.); indefinite pronouns (few, more, each, every, either, all, both, some, any, etc.); and demonstrative pronouns. The demonstratives (this, that, these, those, such) are discussed in the section on Demonstrative Pronouns. Notice that the possessive nouns differ from the other determiners in that they, themselves, are often accompanied by other determiners: "my mother's rug," "the priests's collar," "a dog's life."
This categorization of determiners is based on Understanding English Grammar by Martha Kolln. 4rth Edition. MacMillan Publishing Company: New York. 1994.
Some Notes on Quantifiers
Like articles, quantifiers are words that precede and modify nouns. They tell us how many or how much. Selecting the correct quantifier depends on your understanding the distinction between Count and Non-Count Nouns. For our purposes, we will choose the count noun trees and the non-count noun dancing:
#The following quantifiers will work with count nouns:
many trees
a few trees
few trees
several trees
a couple of trees
none of the trees
#The following quantifiers will work with non-count nouns:
not much dancing
a little dancing
little dancing
a bit of dancing
a good deal of dancing
a great deal of dancing
no dancing
#The following quantifiers will work with both count and non-count nouns:
all of the trees/dancing
some trees/dancing
most of the trees/dancing
enough trees/dancing
a lot of trees/dancing
lots of trees/dancing
plenty of trees/dancing
a lack of trees/dancing
In formal academic writing, it is usually better to use many and much rather than phrases such as a lot of, lots of and plenty of.
There is an important difference between "a little" and "little" (used with non-count words) and between "a few" and "few" (used with count words). If I say that Tashonda has a little experience in management that means that although Tashonda is no great expert she does have some experience and that experience might well be enough for our purposes. If I say that Tashonda has little experience in management that means that she doesn't have enough experience. If I say that Charlie owns a few books on Latin American literature that means that he has some some books — not a lot of books, but probably enough for our purposes. If I say that Charlie owns few books on Latin American literature, that means he doesn't have enough for our purposes and we'd better go to the library.
Unless it is combined with of, the quantifier "much" is reserved for questions and negative statements:
* Much of the snow has already melted.
* How much snow fell yesterday?
* Not much.
Note that the quantifier "most of the" must include the definite article the when it modifies a specific noun, whether it's a count or a non-count noun: "most of the instructors at this college have a doctorate"; "most of the water has evaporated." With a general plural noun, however (when you are not referring to a specific entity), the "of the" is dropped:
* Most colleges have their own admissions policy.
* Most students apply to several colleges.
An indefinite article is sometimes used in conjunction with the quantifier many, thus joining a plural quantifier with a singular noun (which then takes a singular verb):
* Many a young man has fallen in love with her golden hair.
* Many an apple has fallen by October.
Countable Nouns
Uncountable Nouns
-
much
x
I don't have much money.
many
x
-
I don't have many apples.
few*
x
-
We know few people in the area. I would like to get to know more.
a few**
x
-
We know a few people in the area. I know enough people to keep me happy.
little*
-
x
I know little English. I am going to have a problem getting around England.
a little**
-
x
I know a little English, at least enough to get England.
enough
x
x
I have enough money.
plenty
x
x
I have plenty of money.
** a few/a little - means that there are not a lot of something, but there is enough.
* There are a few apples. There are enough apples.
* There are a people at the meeting. There are enough people to hold a meeting. There are not a lot people, at the meeting, but there are enough
* I know a little English. He know enough English to manage.
* I have a little money.
*few/little - means that is not enough of something.
* There are few apples. There are not enough apples.
* There are few people. There are not enough people at the meeting. We can't hold a meeting, because there are not enough people.
* There is little money. We can't buy a lot of expensive food.
* If things for the holiday. I don't have enough money, then we will stay home and have a great time.
* They know little English. They can't get around very well. They don't know enough English to manage.
and Quantifiers
Definition
Articles, determiners, and quantifiers are those little words that precede and modify nouns:
the teacher, a college, a bit of honey, that person, those people, whatever purpose, either way, your choice
Sometimes these words will tell the reader or listener whether we're referring to a specific or general thing (the garage out back; A horse! A horse! My kingdom for a horse!); sometimes they tell how much or how many (lots of trees, several books, a great deal of confusion). The choice of the proper article or determiner to precede a noun or noun phrase is usually not a problem for writers who have grown up speaking English, nor is it a serious problem for non-native writers whose first language is a romance language such as Spanish. For other writers, though, this can be a considerable obstacle on the way to their mastery of English. In fact, some students from eastern European countries — where their native language has either no articles or an altogether different system of choosing articles and determiners — find that these "little words" can create problems long after every other aspect of English has been mastered.
Determiners are said to "mark" nouns. That is to say, you know a determiner will be followed by a noun. Some categories of determiners are limited (there are only three articles, a handful of possessive pronouns, etc.), but the possessive nouns are as limitless as nouns themselves. This limited nature of most determiner categories, however, explains why determiners are grouped apart from adjectives even though both serve a modifying function. We can imagine that the language will never tire of inventing new adjectives; the determiners (except for those possessive nouns), on the other hand, are well established, and this class of words is not going to grow in number. These categories of determiners are as follows: the articles (an, a, the — see below; possessive nouns (Joe's, the priest's, my mother's); possessive pronouns, (his, your, their, whose, etc.); numbers (one, two, etc.); indefinite pronouns (few, more, each, every, either, all, both, some, any, etc.); and demonstrative pronouns. The demonstratives (this, that, these, those, such) are discussed in the section on Demonstrative Pronouns. Notice that the possessive nouns differ from the other determiners in that they, themselves, are often accompanied by other determiners: "my mother's rug," "the priests's collar," "a dog's life."
This categorization of determiners is based on Understanding English Grammar by Martha Kolln. 4rth Edition. MacMillan Publishing Company: New York. 1994.
Some Notes on Quantifiers
Like articles, quantifiers are words that precede and modify nouns. They tell us how many or how much. Selecting the correct quantifier depends on your understanding the distinction between Count and Non-Count Nouns. For our purposes, we will choose the count noun trees and the non-count noun dancing:
#The following quantifiers will work with count nouns:
many trees
a few trees
few trees
several trees
a couple of trees
none of the trees
#The following quantifiers will work with non-count nouns:
not much dancing
a little dancing
little dancing
a bit of dancing
a good deal of dancing
a great deal of dancing
no dancing
#The following quantifiers will work with both count and non-count nouns:
all of the trees/dancing
some trees/dancing
most of the trees/dancing
enough trees/dancing
a lot of trees/dancing
lots of trees/dancing
plenty of trees/dancing
a lack of trees/dancing
In formal academic writing, it is usually better to use many and much rather than phrases such as a lot of, lots of and plenty of.
There is an important difference between "a little" and "little" (used with non-count words) and between "a few" and "few" (used with count words). If I say that Tashonda has a little experience in management that means that although Tashonda is no great expert she does have some experience and that experience might well be enough for our purposes. If I say that Tashonda has little experience in management that means that she doesn't have enough experience. If I say that Charlie owns a few books on Latin American literature that means that he has some some books — not a lot of books, but probably enough for our purposes. If I say that Charlie owns few books on Latin American literature, that means he doesn't have enough for our purposes and we'd better go to the library.
Unless it is combined with of, the quantifier "much" is reserved for questions and negative statements:
* Much of the snow has already melted.
* How much snow fell yesterday?
* Not much.
Note that the quantifier "most of the" must include the definite article the when it modifies a specific noun, whether it's a count or a non-count noun: "most of the instructors at this college have a doctorate"; "most of the water has evaporated." With a general plural noun, however (when you are not referring to a specific entity), the "of the" is dropped:
* Most colleges have their own admissions policy.
* Most students apply to several colleges.
An indefinite article is sometimes used in conjunction with the quantifier many, thus joining a plural quantifier with a singular noun (which then takes a singular verb):
* Many a young man has fallen in love with her golden hair.
* Many an apple has fallen by October.
Countable Nouns
Uncountable Nouns
-
much
x
I don't have much money.
many
x
-
I don't have many apples.
few*
x
-
We know few people in the area. I would like to get to know more.
a few**
x
-
We know a few people in the area. I know enough people to keep me happy.
little*
-
x
I know little English. I am going to have a problem getting around England.
a little**
-
x
I know a little English, at least enough to get England.
enough
x
x
I have enough money.
plenty
x
x
I have plenty of money.
** a few/a little - means that there are not a lot of something, but there is enough.
* There are a few apples. There are enough apples.
* There are a people at the meeting. There are enough people to hold a meeting. There are not a lot people, at the meeting, but there are enough
* I know a little English. He know enough English to manage.
* I have a little money.
*few/little - means that is not enough of something.
* There are few apples. There are not enough apples.
* There are few people. There are not enough people at the meeting. We can't hold a meeting, because there are not enough people.
* There is little money. We can't buy a lot of expensive food.
* If things for the holiday. I don't have enough money, then we will stay home and have a great time.
* They know little English. They can't get around very well. They don't know enough English to manage.
Selasa, 13 Oktober 2009
Voice Over IP
Voice over Internet Protocol (juga disebut VoIP, IP Telephony, Internet telephony atau Digital Phone) adalah teknologi yang memungkinkan percakapan suara jarak jauh melalui media internet. Data suara diubah menjadi kode digital dan dialirkan melalui jaringan yang mengirimkan paket-paket data, dan bukan lewat sirkuit analog telepon biasa.
Definisi VoIP adalah suara yang dikirim melalui protokol internet (IP).
Perbandingan dengan jaringan suara konvensional
Pada jaringan suara konvesional pesawat telepon langsung terhubung dengan PABX (Privat Automated Branch exchange) atau jika milik TELKOM terhubung langsung dengan STO (Sentral telepon Otomat) terdekat. Dalam STO ini ada daftar nomor-nomor telepon yang disusun secara bertingkat sesuai dengan daerah cakupannya. Jika dari pesawat telepon tersebut mau menghubungi rekan yang lain maka tuts pesawat telepon yang ditekan akan menginformasikan lokasi yang dituju melalui nada-nada DTMF, kemudian jaringan akan secara otomatis menghubungkan kedua titik tersebut.
Bentuk paling sederhana dalam sistem VoIP adalah dua buah komputer terhubung dengan internet. Syarat-syarat dasar untuk mengadakan koneksi VoIP adalah komputer yang terhubung ke internet, mempunyai kartu suara yang dihubungkan dengan speaker dan mikropon. Dengan dukungan perangkat lunak khusus, kedua pemakai komputer bisa saling terhubung dalam koneksi VoIP satu sama lain.
Bentuk hubungan tersebut bisa dalam bentuk pertukaran file, suara, gambar. Penekanan utama untuk dalam VoIP adalah hubungan keduanya dalam bentuk suara. Jika kedua lokasi terhubung dengan jarak yang cukup jauh (antar kota, antar negara) maka bisa dilihat keuntungan dari segi biaya. Kedua pihak hanya cukup membayar biaya pulsa internet saja, yang biasanya akan lebih murah daripada biaya pulsa telepon sambungan langsung jarak jauh (SLJJ) atau internasional (SLI).
Pada perkembangannya, sistem koneksi VoIP mengalami evolusi. Bentuk peralatan pun berkembang, tidak hanya berbentuk komputer yang saling berhubungan, tetapi peralatan lain seperti pesawat telepon biasa terhubung dengan jaringan VoIP. Jaringan data digital dengan gateway untuk VoIP memungkinkan berhubungan dengan PABX atau jaringan analog telepon biasa. Komunikasi antara komputer dengan pesawat (extension) di kantor adalah memungkinkan. Bentuk komunikasi bukan Cuma suara saja. Bisa berbentuk tulisan (chating) atau jika jaringannya cukup besar bisa dipakai untuk Video Conference. Dalam bentuk yang lebih lanjut komunikasi ini lebih dikenal dengan IP Telephony yang merupakan komunikasi bentuk multimedia sebagai kelanjutan bentuk komunkasi suara (VoIP). Keluwesan dari VoIP dalam bentuk jaringan, peralatan dan media komunikasinya membuat VoIP menjadi cepat popular di masyarakat umum.
Khusus untuk VoIP bentuk primitif dari jaringan adalah PC ke PC. Dengan memakai PC yang ada soundcardnya dan terhubung dengan jaringan maka sudah bisa dilakukan kegiatan VoIP . Perkembangan berikutnya adalah pengabungan jaringan PABX dengan jaringan VoIP. Disini dibutuhkan VoIP gateway. Gambarannya adalah lawan bicara menggunakan komputer untuk menghubungi sebuah office yang mempunyai VoIP gateway. Pengembangan lebih jauh dari konfigurasi ini berbentuk penggabungan PABX antara dua lokasi dengan menggunakan jaringan VoIP. Tidak terlalu dipedulin bentuk jaringan selama memakai protocol TCP/IP maka kedua lokasi bisa saling berhubungan. Yang paling komplek adalah bentuk jaringan yang menggunakan semua kemungkinan yang ada dengan berbagai macam bentuk jaringan yang tersedia. Dibutuhkan sedikit tambahan keahlian untuk bentuk jaringan yang komplek seperti itu.
Pada awalnya bentuk jaringan adalah tertutup antar lokasi untuk penggunaan sendiri (Interm, Privat). Bentuk jaringan VoIP kemudian berkembang lebih komplek. Untuk penggunaan antar cabang pada komunikasi internal, VoIP digunakan sebagai penyambung antar PABX. Perkembangan selanjutnya adalah gabungan PABX tersebut tidak lagi menggunakan jaringan tertutup tetapi telah memakai internet sebagai bentuk komunikasi antara kantor tersebut. Tingkat lebih lanjut adalah penggabungan antar jaringan. Dengan segala perkembangannya maka saat ini telah dibuat tingkatan (hirarky) dari jaringan Voip.
Aplikasi VoIP dan Keamanannya
Salah satu aplikasi VoIP yang tersedia adalah Skype. Skype adalah [[software]] aplikasi komunikasi suara berbasis IP melalui internet antara sesama pengguna Skype. Pada saat menggunakan Skype maka pengguna Skype yang sedang online akan mencari pengguna Skype lainnya lalu mulai membangun jaringan untuk menemukan pengguna-pengguna lainnya. Skype memiliki berbagai macam fitur yang dapat memudahkan penggunanya. Skype juga dilengkapi dengan SkypeOut dan SkypeIn yang memungkinkan pengguna Skype untuk berhubungan dengan pengguna telepon konvensional dan telepon genggam.
Skype menggunakan protokol HTTP untuk berkomunikasi dengan Skype server untuk otentikasi username/password dan registrasi dengan Skype directory server. Versi modifikasi dari protokol HTTP digunakan untuk berkomunikasi dengan sesama Skype client. Keuntungan yang dimiliki aplikasi ini adalah tersedianya layanan keamanan dalam pentransmisian data yang berupa suara. Layanan keamanan yang diberikan adalah sebagai berikut :
* Privacy
Skype menggunakan AES (Advanced Encryption Standard) 256-bit untuk proses enkripsi dengan total probabilitas percobaan kunci (brute-force attack) sebanyak 1,1 x E-77 kali, sedangkan untuk proses pertukaran kunci (key exchange) simetriknya menggunakan RSA 1024-bit. Public key pengguna akan disertifikasi oleh Skype server pada saat login dengan menggunakan sertifikat RSA 1536 atau 2048-bit. Skype secara otomatis akan mengenkripsi semua data sebelum ditransmisikan melalui internet.
* Authentication
Setiap pengguna Skype memiliki sebuah username dan sebuah password. Dan setiap username memiliki sebuah alamat e-mail yang teregistrasi. Untuk masuk ke sistem Skype , pengguna harus menyertakan pasangan username dan passwordnya. Jika pengguna lupa password tersebut maka Skype akan mengubahnya dan mengirimkan password yang baru ke alamat e-mail pengguna yang sudah teregistrasi. Pendekatan ini dikenal dengan E-mail Based Identification and Authentication. Dikarenakan Skype merupakan sistem komunikasi suara maka setiap penggunanya dapat secara langsung mengidentifikasi lawan bicaranya melalui suaranya.
Keuntungan VoIP
* Biaya lebih rendah untuk sambungan langsung jarak jauh. Penekanan utama dari VoIP adalah biaya. Dengan dua lokasi yang terhubung dengan internet maka biaya percakapan menjadi sangat rendah.
* Memanfaatkan infrastruktur jaringan data yang sudah ada untuk suara. Berguna jika perusahaan sudah mempunyai jaringan. Jika memungkinkan jaringan yang ada bisa dibangun jaringan VoIP dengan mudah. Tidak diperlukan tambahan biaya bulanan untuk penambahan komunikasi suara.
* Penggunaan bandwidth yang lebih kecil daripada telepon biasa. Dengan majunya teknologi penggunaan bandwidth untuk voice sekarang ini menjadi sangat kecil. Teknik pemampatan data memungkinkan suara hanya membutuhkan sekitar 8kbps bandwidth.
* Memungkinkan digabung dengan jaringan telepon lokal yang sudah ada. Dengan adanya gateway bentuk jaringan VoIP bisa disambungkan dengan PABX yang ada dikantor. Komunikasi antar kantor bisa menggunakan pesawat telepon biasa
* Berbagai bentuk jaringan VoIP bisa digabungkan menjadi jaringan yang besar. Contoh di Indonesia adalah VoIP Rakyat.
* Variasi penggunaan peralatan yang ada, misal dari PC sambung ke telepon biasa, IP phone handset
Kelemahan dari VoIP
* Kualitas suara tidak sejernih Telkom. Merupakan efek dari kompresi suara dengan bandwidth kecil maka akan ada penurunan kualitas suara dibandingkan jaringan PSTN konvensional. Namun jika koneksi internet yang digunakan adalah koneksi internet pita-lebar / broadband seperti Telkom Speedy, maka kualitas suara akan jernih - bahkan lebih jernih dari sambungan Telkom dan tidak terputus-putus.
* Ada jeda dalam berkomunikasi. Proses perubahan data menjadi suara, jeda jaringan, membuat adanya jeda dalam komunikasi dengan menggunakan VoIP. Kecuali jika menggunakan koneksi Broadband (lihat di poin atas).
* Regulasi dari pemerintah RI membatasi penggunaan untuk disambung ke jaringan milik Telkom.
* Jika belum terhubung secara 24 jam ke internet perlu janji untuk saling berhubungan.
* Jika memakai internet dan komputer di belakang NAT (Network Address Translation), maka dibutuhkan konfigurasi khusus untuk membuat VoIP tersebut berjalan
* Tidak pernah ada jaminan kualitas jika VoIP melewati internet.
* Peralatan relatif mahal. Peralatan VoIP yang menghubungkan antara VoIP dengan PABX (IP telephony gateway) relatif berharga mahal. Diharapkan dengan makin populernya VoIP ini maka harga peralatan tersebut juga mulai turun harganya.
* Berpotensi menyebabkan jaringan terhambat/Stuck. Jika pemakaian VoIP semakin banyak, maka ada potensi jaringan data yang ada menjadi penuh jika tidak diatur dengan baik. Pengaturan bandwidth adalah perlu agar jaringan di perusahaan tidak menjadi jenuh akibat pemakaian VoIP.
* Penggabungan jaringan tanpa dikoordinasi dengan baik akan menimbulkan kekacauan dalam sistem penomoran
Komunitas VoIP
Komunitas pengguna / pengembang VoIP di masyarakat, berkembang di tahun 2000. Komunitas awal pengguna / pengembang VoIP adalah “VoIP Merdeka”.”VoIP Merdeka” (VM) dicetuskan oleh Onno W. Purbo. Teknologi yang digunakan oleh "VoIP Merdeka" (VM) adalah H.323 yang merupakan teknologi awal VoIP. Sentral VoIP Merdeka di hosting di Indonesia Internet Exchange (IIX) atas dukungan beberapa ISP dan Asossiasi Penyelenggara Jaringan Internet (APJII). Kode area "VoIP Merdeka" pada saat itu secara aklamasi di tentukan menjadi 6288, tentunya tanpa memperoleh restu dari pemerintah.
Di tahun 2005, Anton Raharja dkk dari ICT Center Jakarta mulai mengembangkan VoIP jenis baru berbasis Session Initiation Protocol (SIP). Teknologi SIP merupakan teknologi pengganti H.323 yang sulit menembus proxy server. Di tahun 2006, infrastruktur VoIP SIP di kenal sebagai VoIP Rakyat.
Kualitas suara
Kualitas suara VoIP dipengaruhi oleh beberapa parameter yaitu kapasitas bandwidth, tingkat hilang paket dan waktu tunda yang terjadi di dalam jaringan. Kapasitas bandwidth adalah ketersediaan sumber daya jaringan dalam bentuk lebar pita yang digunakan untuk mentransmisikan data paket. Tingkat hilang paket adalah parameter yang menyatakan besarnya laju kesalahan yang terjadi sepanjang jalur pengiriman data paket dari pengirim ke penerima. Waktu tunda adalah parameter yang menyatakan rentang waktu yang diperlukan untuk mengirimkan paket dari pengirim ke penerima.
Kesimpulan
Dengan segala potensi yang ada terutama sekali biaya yang relatif murah untuk percakapan jarak jauh, VoIP sangat berpotensi dikembangkan. Paradigma bahwa PSTN adalah inti dari jaringan suara harus dirubah bahwa telepon analog biasa adalah bagian dari IP Telephony, yang mengakibatkan perkembangan IPTelePhony akan jauh berkembang dengan pesat dibandingkan telepon analog biasa.
Memanfaatkan idle bandwidth. Jika perusahaan sudah mempunyai jaringan antar cabang VoIP dapat digunakan tanpa menambah biaya jaringan. Tergantung dari system yang mau dipakai, jika hanya antar PC maka tidak ada investasi tambahan untuk membuat jaringan VoIP. Investasi tambahan yang akan muncul jika jaringan VoIP ini digabung dengan PABX.
Perkembangan VoIP akan makin berkembang menjadi IP Telephony, suatu bentuk komunikasi multimedia. Sebagai Alternatif penggunaan telepon, dengan makin maraknya penggunaan VoIP Merdeka Dari 200 ke 1.300 pengguna dalam 1 bulan pertama. Saat ini 3.000 s.d. 4.000 panggilan dalam sehari. Lebih murah, misalkan biaya internet - TelkomNet Instan +/- Rp
Definisi VoIP adalah suara yang dikirim melalui protokol internet (IP).
Perbandingan dengan jaringan suara konvensional
Pada jaringan suara konvesional pesawat telepon langsung terhubung dengan PABX (Privat Automated Branch exchange) atau jika milik TELKOM terhubung langsung dengan STO (Sentral telepon Otomat) terdekat. Dalam STO ini ada daftar nomor-nomor telepon yang disusun secara bertingkat sesuai dengan daerah cakupannya. Jika dari pesawat telepon tersebut mau menghubungi rekan yang lain maka tuts pesawat telepon yang ditekan akan menginformasikan lokasi yang dituju melalui nada-nada DTMF, kemudian jaringan akan secara otomatis menghubungkan kedua titik tersebut.
Bentuk paling sederhana dalam sistem VoIP adalah dua buah komputer terhubung dengan internet. Syarat-syarat dasar untuk mengadakan koneksi VoIP adalah komputer yang terhubung ke internet, mempunyai kartu suara yang dihubungkan dengan speaker dan mikropon. Dengan dukungan perangkat lunak khusus, kedua pemakai komputer bisa saling terhubung dalam koneksi VoIP satu sama lain.
Bentuk hubungan tersebut bisa dalam bentuk pertukaran file, suara, gambar. Penekanan utama untuk dalam VoIP adalah hubungan keduanya dalam bentuk suara. Jika kedua lokasi terhubung dengan jarak yang cukup jauh (antar kota, antar negara) maka bisa dilihat keuntungan dari segi biaya. Kedua pihak hanya cukup membayar biaya pulsa internet saja, yang biasanya akan lebih murah daripada biaya pulsa telepon sambungan langsung jarak jauh (SLJJ) atau internasional (SLI).
Pada perkembangannya, sistem koneksi VoIP mengalami evolusi. Bentuk peralatan pun berkembang, tidak hanya berbentuk komputer yang saling berhubungan, tetapi peralatan lain seperti pesawat telepon biasa terhubung dengan jaringan VoIP. Jaringan data digital dengan gateway untuk VoIP memungkinkan berhubungan dengan PABX atau jaringan analog telepon biasa. Komunikasi antara komputer dengan pesawat (extension) di kantor adalah memungkinkan. Bentuk komunikasi bukan Cuma suara saja. Bisa berbentuk tulisan (chating) atau jika jaringannya cukup besar bisa dipakai untuk Video Conference. Dalam bentuk yang lebih lanjut komunikasi ini lebih dikenal dengan IP Telephony yang merupakan komunikasi bentuk multimedia sebagai kelanjutan bentuk komunkasi suara (VoIP). Keluwesan dari VoIP dalam bentuk jaringan, peralatan dan media komunikasinya membuat VoIP menjadi cepat popular di masyarakat umum.
Khusus untuk VoIP bentuk primitif dari jaringan adalah PC ke PC. Dengan memakai PC yang ada soundcardnya dan terhubung dengan jaringan maka sudah bisa dilakukan kegiatan VoIP . Perkembangan berikutnya adalah pengabungan jaringan PABX dengan jaringan VoIP. Disini dibutuhkan VoIP gateway. Gambarannya adalah lawan bicara menggunakan komputer untuk menghubungi sebuah office yang mempunyai VoIP gateway. Pengembangan lebih jauh dari konfigurasi ini berbentuk penggabungan PABX antara dua lokasi dengan menggunakan jaringan VoIP. Tidak terlalu dipedulin bentuk jaringan selama memakai protocol TCP/IP maka kedua lokasi bisa saling berhubungan. Yang paling komplek adalah bentuk jaringan yang menggunakan semua kemungkinan yang ada dengan berbagai macam bentuk jaringan yang tersedia. Dibutuhkan sedikit tambahan keahlian untuk bentuk jaringan yang komplek seperti itu.
Pada awalnya bentuk jaringan adalah tertutup antar lokasi untuk penggunaan sendiri (Interm, Privat). Bentuk jaringan VoIP kemudian berkembang lebih komplek. Untuk penggunaan antar cabang pada komunikasi internal, VoIP digunakan sebagai penyambung antar PABX. Perkembangan selanjutnya adalah gabungan PABX tersebut tidak lagi menggunakan jaringan tertutup tetapi telah memakai internet sebagai bentuk komunikasi antara kantor tersebut. Tingkat lebih lanjut adalah penggabungan antar jaringan. Dengan segala perkembangannya maka saat ini telah dibuat tingkatan (hirarky) dari jaringan Voip.
Aplikasi VoIP dan Keamanannya
Salah satu aplikasi VoIP yang tersedia adalah Skype. Skype adalah [[software]] aplikasi komunikasi suara berbasis IP melalui internet antara sesama pengguna Skype. Pada saat menggunakan Skype maka pengguna Skype yang sedang online akan mencari pengguna Skype lainnya lalu mulai membangun jaringan untuk menemukan pengguna-pengguna lainnya. Skype memiliki berbagai macam fitur yang dapat memudahkan penggunanya. Skype juga dilengkapi dengan SkypeOut dan SkypeIn yang memungkinkan pengguna Skype untuk berhubungan dengan pengguna telepon konvensional dan telepon genggam.
Skype menggunakan protokol HTTP untuk berkomunikasi dengan Skype server untuk otentikasi username/password dan registrasi dengan Skype directory server. Versi modifikasi dari protokol HTTP digunakan untuk berkomunikasi dengan sesama Skype client. Keuntungan yang dimiliki aplikasi ini adalah tersedianya layanan keamanan dalam pentransmisian data yang berupa suara. Layanan keamanan yang diberikan adalah sebagai berikut :
* Privacy
Skype menggunakan AES (Advanced Encryption Standard) 256-bit untuk proses enkripsi dengan total probabilitas percobaan kunci (brute-force attack) sebanyak 1,1 x E-77 kali, sedangkan untuk proses pertukaran kunci (key exchange) simetriknya menggunakan RSA 1024-bit. Public key pengguna akan disertifikasi oleh Skype server pada saat login dengan menggunakan sertifikat RSA 1536 atau 2048-bit. Skype secara otomatis akan mengenkripsi semua data sebelum ditransmisikan melalui internet.
* Authentication
Setiap pengguna Skype memiliki sebuah username dan sebuah password. Dan setiap username memiliki sebuah alamat e-mail yang teregistrasi. Untuk masuk ke sistem Skype , pengguna harus menyertakan pasangan username dan passwordnya. Jika pengguna lupa password tersebut maka Skype akan mengubahnya dan mengirimkan password yang baru ke alamat e-mail pengguna yang sudah teregistrasi. Pendekatan ini dikenal dengan E-mail Based Identification and Authentication. Dikarenakan Skype merupakan sistem komunikasi suara maka setiap penggunanya dapat secara langsung mengidentifikasi lawan bicaranya melalui suaranya.
Keuntungan VoIP
* Biaya lebih rendah untuk sambungan langsung jarak jauh. Penekanan utama dari VoIP adalah biaya. Dengan dua lokasi yang terhubung dengan internet maka biaya percakapan menjadi sangat rendah.
* Memanfaatkan infrastruktur jaringan data yang sudah ada untuk suara. Berguna jika perusahaan sudah mempunyai jaringan. Jika memungkinkan jaringan yang ada bisa dibangun jaringan VoIP dengan mudah. Tidak diperlukan tambahan biaya bulanan untuk penambahan komunikasi suara.
* Penggunaan bandwidth yang lebih kecil daripada telepon biasa. Dengan majunya teknologi penggunaan bandwidth untuk voice sekarang ini menjadi sangat kecil. Teknik pemampatan data memungkinkan suara hanya membutuhkan sekitar 8kbps bandwidth.
* Memungkinkan digabung dengan jaringan telepon lokal yang sudah ada. Dengan adanya gateway bentuk jaringan VoIP bisa disambungkan dengan PABX yang ada dikantor. Komunikasi antar kantor bisa menggunakan pesawat telepon biasa
* Berbagai bentuk jaringan VoIP bisa digabungkan menjadi jaringan yang besar. Contoh di Indonesia adalah VoIP Rakyat.
* Variasi penggunaan peralatan yang ada, misal dari PC sambung ke telepon biasa, IP phone handset
Kelemahan dari VoIP
* Kualitas suara tidak sejernih Telkom. Merupakan efek dari kompresi suara dengan bandwidth kecil maka akan ada penurunan kualitas suara dibandingkan jaringan PSTN konvensional. Namun jika koneksi internet yang digunakan adalah koneksi internet pita-lebar / broadband seperti Telkom Speedy, maka kualitas suara akan jernih - bahkan lebih jernih dari sambungan Telkom dan tidak terputus-putus.
* Ada jeda dalam berkomunikasi. Proses perubahan data menjadi suara, jeda jaringan, membuat adanya jeda dalam komunikasi dengan menggunakan VoIP. Kecuali jika menggunakan koneksi Broadband (lihat di poin atas).
* Regulasi dari pemerintah RI membatasi penggunaan untuk disambung ke jaringan milik Telkom.
* Jika belum terhubung secara 24 jam ke internet perlu janji untuk saling berhubungan.
* Jika memakai internet dan komputer di belakang NAT (Network Address Translation), maka dibutuhkan konfigurasi khusus untuk membuat VoIP tersebut berjalan
* Tidak pernah ada jaminan kualitas jika VoIP melewati internet.
* Peralatan relatif mahal. Peralatan VoIP yang menghubungkan antara VoIP dengan PABX (IP telephony gateway) relatif berharga mahal. Diharapkan dengan makin populernya VoIP ini maka harga peralatan tersebut juga mulai turun harganya.
* Berpotensi menyebabkan jaringan terhambat/Stuck. Jika pemakaian VoIP semakin banyak, maka ada potensi jaringan data yang ada menjadi penuh jika tidak diatur dengan baik. Pengaturan bandwidth adalah perlu agar jaringan di perusahaan tidak menjadi jenuh akibat pemakaian VoIP.
* Penggabungan jaringan tanpa dikoordinasi dengan baik akan menimbulkan kekacauan dalam sistem penomoran
Komunitas VoIP
Komunitas pengguna / pengembang VoIP di masyarakat, berkembang di tahun 2000. Komunitas awal pengguna / pengembang VoIP adalah “VoIP Merdeka”.”VoIP Merdeka” (VM) dicetuskan oleh Onno W. Purbo. Teknologi yang digunakan oleh "VoIP Merdeka" (VM) adalah H.323 yang merupakan teknologi awal VoIP. Sentral VoIP Merdeka di hosting di Indonesia Internet Exchange (IIX) atas dukungan beberapa ISP dan Asossiasi Penyelenggara Jaringan Internet (APJII). Kode area "VoIP Merdeka" pada saat itu secara aklamasi di tentukan menjadi 6288, tentunya tanpa memperoleh restu dari pemerintah.
Di tahun 2005, Anton Raharja dkk dari ICT Center Jakarta mulai mengembangkan VoIP jenis baru berbasis Session Initiation Protocol (SIP). Teknologi SIP merupakan teknologi pengganti H.323 yang sulit menembus proxy server. Di tahun 2006, infrastruktur VoIP SIP di kenal sebagai VoIP Rakyat.
Kualitas suara
Kualitas suara VoIP dipengaruhi oleh beberapa parameter yaitu kapasitas bandwidth, tingkat hilang paket dan waktu tunda yang terjadi di dalam jaringan. Kapasitas bandwidth adalah ketersediaan sumber daya jaringan dalam bentuk lebar pita yang digunakan untuk mentransmisikan data paket. Tingkat hilang paket adalah parameter yang menyatakan besarnya laju kesalahan yang terjadi sepanjang jalur pengiriman data paket dari pengirim ke penerima. Waktu tunda adalah parameter yang menyatakan rentang waktu yang diperlukan untuk mengirimkan paket dari pengirim ke penerima.
Kesimpulan
Dengan segala potensi yang ada terutama sekali biaya yang relatif murah untuk percakapan jarak jauh, VoIP sangat berpotensi dikembangkan. Paradigma bahwa PSTN adalah inti dari jaringan suara harus dirubah bahwa telepon analog biasa adalah bagian dari IP Telephony, yang mengakibatkan perkembangan IPTelePhony akan jauh berkembang dengan pesat dibandingkan telepon analog biasa.
Memanfaatkan idle bandwidth. Jika perusahaan sudah mempunyai jaringan antar cabang VoIP dapat digunakan tanpa menambah biaya jaringan. Tergantung dari system yang mau dipakai, jika hanya antar PC maka tidak ada investasi tambahan untuk membuat jaringan VoIP. Investasi tambahan yang akan muncul jika jaringan VoIP ini digabung dengan PABX.
Perkembangan VoIP akan makin berkembang menjadi IP Telephony, suatu bentuk komunikasi multimedia. Sebagai Alternatif penggunaan telepon, dengan makin maraknya penggunaan VoIP Merdeka Dari 200 ke 1.300 pengguna dalam 1 bulan pertama. Saat ini 3.000 s.d. 4.000 panggilan dalam sehari. Lebih murah, misalkan biaya internet - TelkomNet Instan +/- Rp
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