Teknologi wireless merupakan peralatan untuk berkomunikasi tanpa koneksi fisik. Pada teknologi wireless ini menggunakan transmisi frekwensi radio sebagai alat untuk mengirimkan datanya.

Jaringan wireless merupakan jaringan tanpa kabel yang menggunakan gelombang radio sebagai media transmisi data. Pengelompokkan jaringan wireless berdasarkan jaringannya ada 3 macam, yaitu : Wireless Wide Area Network (WWAN), WLAN, dan Wireless Personal Area  Network (WPAN).

• Keuntungannya

Keuntungan yang akan dirasakan oleh user dengan adanya wireless untuk koneksi internet, yaitu user dapat melakukan koneksi internet kapan saja dan dimana saja asalkan masih berada dalam ruang lingkup hot-spot, selain itu dalam segi biaya pembangunan, wireless jauh lebih murah bila dibandingkan dengan kabel.

• Kelemahannya

Selain itu jaringan wireless juga memiliki lebih banyak kelemahan dibanding dengan jaringan kabel. Secara umum kelemahan jaringan wireless terdapat pada konfigurasi dan jenis enkripsi yang digunakan. Salah satu penyebab kelemahan pada konfigurasi dikarenakan saat ini untuk membangun sebuah jaringan wireless cukup mudah maka banyak vendor yang memudahkan pengguna atau admin jaringan sehingga sering ditemukan wireless yang masih menggunakan konfigurasi wireless default bawaan vendor. Contohnya sering ditemukan wireless yang dipasang pada jaringan setting defaultnya seperti SSID, IP Address , remote manajemen, DHCP enable, kanal frekuensi masih bawaan darri vendor.

WEP (Wired Equivalent Privacy) yang menjadi standart keamanan wireless sebelumnya, saat ini dapat dengan mudah dipecahkan dengan berbagai tools yang tersedia gratis di internet. WPA-PSK dan LEAP yang dianggap menjadi solusi menggantikan WEP, saat ini juga sudah dapat dipecahkan dengan metode dictionary attack secara offline.

• Pengamanan pada jaringan wireless

Untuk menghindari jaringan wireless di hack maka diperlukan pengamanan pada jaringan wireless, diantaranya adalah :

1.    Memakai Enkripsi.

Enkripsi merupakan ukuran security yang pertama, tetapi banyak wireless access points (WAP) tidak menggunakan enkripsi sebagai defaultnya. Kenyataannya 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.    Pakai Enkripsi yang Kuat.

Karena kelemahan kelemahan yang ada di WEP, maka dianjurkan untuk menggunakan juga Wi-Fi Protected Access (WPA). Untuk memakai WPA, WAP harus men-supportnya. Sisi client juga harus dapat men-support WPA tsb.

3.    Ganti Default Password Administrator.
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.    Mematikan 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.
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.

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.

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.

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.

Misal dalam lingkup fakultas.

Pada strategi penahapan, perencanaan secara umum disiapkan secara

menyeluruh selangkah demi selangkah. Misalnya dikembangkan antar fakultas.

Dalam strategi serentak,implementasinya dilakukan secara serentak dan menyeluruh. Untuk  sampai ketahap ini perlu hasil dari suatu kajian model yang telah digagas dalam tahap terbatas dan pentahapan.

Tujuan penyelenggaran video konferensi untuk perluasan akses terhadap pusat dan sumber belajar dalam proses pembelajaran. Dalam takaran konsep,teknologi video conferensi digunakan sebagai salah satu cara penyampaian dalam proses,pembelajaran berbasis elektronik. Sehingga video conferensi dalam konteks ini dirancang untuk tujuan instruksional. Teknologi video konferensi untuk tujuan pembelajaran sifatnya lebih khusus dan spesifik karena model ini berangkat dari kebutuhan pembelajaran yang mulai tahap perencanaan, perancangan, implementasi dan evaluasi berpatokan pada kebutuhan pembelajar sesuai tuntutan kurikulum institusi yang mengembangkan.

Fungsi video conference dalam pembelajaran

Fungsi video conference dalam proses pembelajaran dalam suatu institusi dapat dibedakan secara konseptual dan operasional.

Fungsi konseptual meliputi fungsi pengayaan,pengganti, pengajaran langsung dan penggerak (motivator).

Dalam fungsi pengayaan konferensi berbasis video dapat menyajikan bahan tambahan yang tidak dapat diberikan oleh pendidik, bahan tambahan ini bisa saja untuk memantapkan apa yang sebelumnya pernah diperoleh atau sekedar meningkatkan dan memperkaya perbendaharaan kasanah informasi yang relevan dengan tujuan pembelajaran.

Dalam fungsi pengganti Program konferensi berbasis video, dapat pula menyajikan hal-hal yang tidak dapat diperoleh oleh dari para pendidik, seperti misalnya menampilkan tokoh untuk meningkatkan tarik dan aksentuasi, penyajian peristiwa masa lalu,. Sedangkan video konferensi dalam fungsi pengajaran langsung biasanya dikemas untuk suatu tujuan khusus yang dinyatakan eksplisit.

Sedang dalam fungsinya yang terakhir penyelenggaran video konferensi dalam pembelajaran untuk fungsi penggerak. Dalam konteks ini program video konferensi dapat menampilkan rangsangan untuk suatu tindakan positif dalam meningkatkan pengetahuan, keterampilan dan sikap. Misalnya siaran format video realtime tentang suatu tokoh dalam pembelajaran yang terkenal akan inovasinya.

Komponens Sistem Video konferensi

sebuah sistem harus dibangun oleh beberapa komponen yang saling bersinergi,

berkolaborasi akan suatu tujuan, maka dalam penyelenggaran video konferensi persoalan pada

insfrastruktur, sarana dan prasarana sudah tidak menjadi persoalan lagi. Dalam konteks ini

persepsi dalam penyelenggaran video konferensi untuk memperluas akses terhadap pusat dan

sumber belajar menjadi garapan sangat serius pada komponen

1. hardware

2. insfrastruktur jaringan ( fisik dan logik)

3. software

4. materi

5. strategi interaksi, dan

6. pemeran

Konsep pembelajaran konvesional versus elektronik.

As indicated in the tables below, many determiners can be used either as adjectives or as pronouns. As will be pointed out in the next chapter, when a determiner is used as an adjective modifying a noun, the determiner usually precedes any other adjectives modifying the same noun.

The use of the following determiners has already been discussed in previous chapters: a, an, the, this, that, these and those. The possessive adjectives my, your, his, her, our and their can also be classified as determiners.

As indicated below, many determiners may be used only with certain types of noun. In the following tables, the abbreviation CN stands for Countable Noun, and the abbreviation UN stands for Uncountable Noun. In these tables, the noun tree is used as an example of a countable noun, and the noun grass is used as an example of an uncountable noun.

Determiners used as Adjectives

The following determiners can be used independently, as pronouns:

Determiners used as Pronouns

Determiners used to refer to groups of two persons or things

In Old English, there were singular forms, plural forms and dual forms. Dual forms are used to refer to two persons or things. In modern English, a few words still remain which refer to two persons or things.
For example, the determiners both, either and neither are used when referring to groups of two. Both refers to two things of a group of two, either refers to one thing of a group of two, and neither refers to zero things of a group of two.
e.g. I have two brothers. Both of them are engineers.
I had two maps of the city, but I cannot find either of them.
There are two textbooks for the course. Neither of them is expensive.

In contrast, the determiners all, any and none may be used when referring to groups with more than two members. All may refer to every member of a group of three or more, any may refer to one member of a group of three or more, and none may refer to zero members of a group of three or more.
e.g. I have three brothers. All of them are engineers.
I had four maps of the city, but I cannot find any of them.
There are six textbooks for the course. None of them is expensive.

See Exercise 1.

The following rules for the use of either and neither should be noted.

If it is desired to change a clause beginning with either so as to express a negative meaning, either must be changed to neither.
e.g. Affirmative Meaning: Either of the alternatives is acceptable.
Negative Meaning: Neither of the alternatives is acceptable.

Affirmative Meaning: Either hotel will offer you its best room.
Negative Meaning: Neither hotel will offer you its best room.

A sentence which contains the word either, in which either does not occur at the beginning of a clause, can be changed to express a negative meaning either by using the word not, or by changing either to neither.
e.g. Affirmative Meaning: You may borrow either of the books.
Negative Meaning: You may not borrow either of the books.
Negative Meaning: You may borrow neither of the books.

Affirmative Meaning: I might give the message to either boy.
Negative Meaning: I might not give the message to either boy.
Negative Meaning: I might give the message to neither boy.

It should be noted that in modern English, the determiner neither is most often used only at the beginning of a clause. Otherwise, the meaning of neither is usually expressed by the combination not … either.

In addition to being used as determiners, the words both, either and neither can also be used as conjunctions. Conjunctions will be discussed in Chapter 28.

Determiners used as singular or plural pronouns

In formal English, the pronouns another, each, either, neither and one always take singular verbs.
e.g. Each of the children wants to win the prize.
Either of the alternatives is acceptable.
Neither of the books has good illustrations.
Every one of the students was ready on time.
In these examples, the singular verbs wants, is, has, and was are used with the pronouns each, either, neither and one.

In informal English, plural verbs are sometimes used with pronouns such as each, either and neither.
e.g. Neither of the books have good illustrations.
However, this use of the plural verb is considered to be grammatically incorrect in formal English.

It should also be noted that in formal English, when the words another, each, every, either, neither and one are used in combination with personal pronouns or possessive adjectives, singular forms are always used. As mentioned previously, in formal English, the adjective his or the phrase his or her may be used when referring to a group containing both male and female members.
e.g. Each of the children waited impatiently for his turn.
Every student raised his or her hand.
Neither of the girls has finished her homework.
Either of the hotels will offer you its best room.
In these examples, each, every, neither and either are used in combination with the singular forms his, his or her, her and its.

In informal English, plural possessive adjectives are often used in this type of sentence.
e.g. Neither of the girls finished their homework.
However, this use of the plural possessive adjective is considered to be grammatically incorrect in formal English.

It should be noted that in both formal and informal English, none is used sometimes with singular, and sometimes with plural verbs.
e.g. None of them is here. or
None of them are here.

In contrast, the pronouns both, few, many and several are always plural. They take plural verbs, and are used in combination with plural personal pronouns and possessive adjectives. In addition, the pronoun all is always plural when used with countable nouns.
e.g. Both of the boys have completed their essays.
Several of the musicians are giving their first performances tonight.
All of the girls have finished their homework.

In these examples, the pronouns both, several and all take the plural verbs have completed, are giving and have finished, and are used in combination with the plural possessive adjective their.

Function

In most Indo-European languages, determiners are either independent words or clitics that precede the rest of the noun phrase. In other languages, determiners are prefixed or suffixed to the noun, or even change the noun’s form. For example, in Swedish bok “book”, when definite, becomes boken “the book” (suffixed definite articles are common in Scandinavian languages).

In some constructions, such as those which use the names of school subjects (“Physics uses mathematics”), a determiner is not used. This condition is called the “zero determiner” instance.

X-bar theory contends that every noun has a corresponding determiner. In a case where a noun does not have a pronounced determiner, X-bar theory hypothesizes the presence of a zero article.

English determiners

The determiner function is usually performed by the determiner class of words, but can also be filled by words from other entities:

1. Basic determiners are words from the determiner class (e.g. the girl, those pencils) or determiner phrases (e.g. almost all people, more than two problems).
2. Subject determiners are possessive noun phrases (e.g. his daughter, the boy’s friend).
3. Minor determiners are plain NPs (e.g. what colour carpet, this size shoes) and prepositional phrases (under twenty meters, up to twelve people).

Determiner Class

A determiner establishes the reference of a noun or noun phrase, including quantity, rather than its attributes as expressed by adjectives. Despite this tendency, determiners have a variety of functions including, in English, modifiers in adjective phrases and determiner phrases, and even markers of coordination.

This word class, or part of speech, exists in many languages, including English, though most English dictionaries still classify determiners under other parts of speech. Determiners usually include articles, and may include items like demonstratives, possessive determiners, quantifiers, and cardinal numbers, depending on the language.

English determiners

Determiners, in English, form a closed class of words that number (exclusive of cardinal numerals) about 50 and include^[1]:

• Alternative-additive Determiners: another, other, somebody else
• Articles: a, an, the
• Cardinal Numbers: one, two, fifty, etc.
• Degree Determiners: many, much, few, little…
• Demonstratives: this, that, these, those, which
• Disjunctive Determiners: either, neither
• Distributive Determiners: each, every
• Elective Determiners: any, either, wichever
• Equative Determiners: the same
• Evaluative Determiners: such
• Exclamative Determiners: what eyes!
• Existential Determiners: some, any
• Interrogative and Relative Determiners: which, what, whichever, whatever
• Negative Determiners: no, neither
• Personal Determiners: we teachers, you guys
• Positive-multal Determiners: a lot of, many, several
• Positive-paucal Determiners: a few, a little, some
• Possessive Determiners: my, your, our, etc.
• Qualitative Determiners: that, so
• Quantifiers: all, few, many, several, some, every, each, any, no, etc.
• Sufficiency Determiners: enough, sufficient
• Uniquitive Determiners: the only
• Universal Determiners: all, both

The two categories into which every one of these determiners can be classified are those of the definite determiners, which limit their reference back to a specific already mentioned entity, and the indefinite determiners, which broaden their referent to one which has not been previously specified, or has just been newly introduced into discourse.

While many words belong to this lexical category exclusively, others belong to a number of categories, for example, the pronoun what in What is good as opposed to the determiner what in what one is good. While numerals exist as nouns, it is debated whether numerals are determiners or not^[2]. For instance, the English numerals for 100 or larger need a determiner, such as “a hundred men.” Similarly, while pronouns like my, your, etc. function as determiners in a noun phrase, many grammars do not make the distinction between class and function and so lump these in with determiners.

Differences from adjectives

Traditional English grammar does not include determiners and calls most determiners adjectives. There are, however, a number of key differences between determiners and adjectives.

1. In English, articles, demonstratives, and possessive determiners cannot co-occur in the same phrase, while any number of adjectives are typically allowed.
   1. A big, green, expensive English book
   2. * The his book
2. Most determiners cannot occur alone in predicative complement position; most adjectives can.
   1. He is happy.
   2. * He is the.
3. Most determiners are not gradable, while adjectives typically are.
   1. happy, happier, happiest
4. Some determiners have corresponding pronouns, while adjectives don’t.
   1. Each likes something different.
   2. * Big likes something different.
5. Adjectives can modify singular or plural nouns, while some determiners can only modify one or the other.
   1. a big person / big people
   2. many people / * many person
6. Adjectives are never obligatory, while determiners often are.

Differences from pronouns

Determiners such as this, all, and some can often occur without a noun. In traditional grammar, these are called pronouns. There are, however, a number of key differences between such determiners and pronouns.

1. Pronouns may occur in tag questions. Determiners cannot.
   1. This is delicious, isn’t it?
   2. *This is delicious, isn’t this?
2. In phrasal verbs, pronouns must appear between the verb and particle. Determiners may occur after the particle.
   1. pick it up
   2. *pick up it
   3. pick this up
   4. pick up this
3. Pronouns all have distinct genitive forms. Determiners do not.
   1. This is mine/yours/theirs.
   2. *This is all’s.

Other realisations

In English, and in many other Indo-European languages, determiners are either independent words or clitics that precede the rest of the noun phrase. Not all languages, however, have a lexically distinct class of determiners. Determiner functions are sometimes realized morphologically as affixes on the noun, or by changing the noun’s form. For example, Swedish bok (“book”), when definite, becomes boken (“the book”). Definite article suffixes are also found in the other North Germanic languages, in Romanian, and in Bulgarian.

Definition.

An article is a limiting word, not descriptive, which cannot be used alone, but always joins to a substantive word to denote a particular thing, or a group or class of things, or any individual of a group or class.

Kinds.

Articles are either definite or indefinite.

The is the definite article, since it points out a particular individual, or group, or class.

An or a is the indefinite article, because it refers to any one of a group or class of things.

An and a are different forms of the same word, the older ān.

Their origin.

The article the comes from an old demonstrative adjective (sē, sēo, ðat, later thē, thēo, that) which was also an article in Old English. In Middle English the became an article, and that remained a demonstrative adjective.

An or a came from the old numeral ān, meaning one.

Two relics.

Our expressions the one, the other, were formerly that one, that other; the latter is still preserved in the expression, in vulgar English, the tother. Not only this is kept in the Scotch dialect, but the former is used, these occurring as the tane, the tother, or the tane, the tither; for example,—

We ca’ her sometimes the tane, sometimes the tother.—Scott.

An before vowel sounds, a before consonant sounds.

Ordinarily an is used before vowel sounds, and a before consonant sounds. Remember that a vowel sound does not necessarily mean beginning with a vowel, nor does consonant sound mean beginning with a consonant, because English spelling does not coincide closely with the sound of words. Examples: “a house,” “an orange,” “a European,” “an honor,” “a yelling crowd.”

An with consonant sounds.

Many writers use an before h, even when not silent, when the word is not accented on the first syllable.

An historian, such as we have been attempting to describe, would indeed be an intellectual prodigy.—Macaulay.

The Persians were an heroic people like the Greeks.—Brewer.

He [Rip] evinced an hereditary disposition to attend to anything else but his business.—Irving.

An habitual submission of the understanding to mere events and images.—Coleridge.

An hereditary tenure of these offices.—Thomas Jefferson.

An article is a little word that comes before a noun. There are two kinds of articles: definite articles and indefinite articles.

In English there is just one definite article: “the”. There are two indefinite articles: “a” and “an”. The word “an” is used before a word starting with a vowel sound: we say “a horse”, “a child”, “a European” (Euro has a “Y” sound), “a university”, but “an orange”, “an elephant”.

Some languages have more than one word for “the”. This is because each noun is either masculine or feminine or, in some languages it can be masculine, feminine or neuter. For example: in French “le” is used for masculine nouns (“le jardin” – “the garden”) and “la” for feminine nouns (“la table” – “the table”). “The” becomes “les” in front of plural nouns. The indefinite articles in French are “un” (masculine) and “une” (feminine). German and Dutch have masculine, feminine and neuter nouns, but in the case of Dutch the word for “the” is the same for masculine and feminine (“de”) so you do not need to know which it is.

Some languages (for example: Russian and Japanese) do not have articles. When speakers of these languages are learning English, it is often difficult to explain to them what an article is. English speakers use them automatically.

In general: “the” in English is used for something you have already been talking about. The word “a” is used when introducing a new idea:

“The tired woman was looking for her cat. Suddenly she saw the cat up a tree”. (We are already talking about the cat. The tree is a new idea).

“The tired woman was walking along when she suddenly saw a cat up a tree”. (She had not been thinking about cats until then).

Sometimes we do not need an article, for example when talking about something in general:

“The dogs do not bite” (meaning: Mr Smith’s dogs). “Barking dogs do not bite” (barking dogs in general).

The words another, other, others and else are used to indicate one or more additional or different things.

Another is formed from a combination of the words an and other, and has a meaning similar to one other. When used as an adjective, another can precede only a singular countable noun. When used as a pronoun, another takes a singular verb.
e.g. Please bring me another knife.
Another of her uncles lives in Montreal.
In the first example, another modifies the singular noun knife. In the second example, the pronoun another is the subject of the singular verb lives.

Other can be used with singular countable, plural countable or uncountable nouns.
e.g. The other door is open.
The other streets are paved.
Do you have any other luggage?
In these examples, other modifies the singular countable noun door, the plural countable noun streets, and the uncountable noun luggage.

Another usually cannot be immediately preceded by a determiner. In contrast, when used before a singular countable noun, other usually must be preceded by a determiner.
e.g. Please pass me the other cup.
I do not know any other way to do it.
There must be some other explanation.
In these examples, other is used with the singular countable nouns cup, way and explanation, and is preceded by the determiners the, any and some.

When other modifies a singular countable noun, the noun is sometimes omitted, particularly in the expression one … the other.
e.g. I have two pens. One is green and the other is blue.
One of my parents is a teacher; the other is a doctor.

In these examples, the nouns following the word other are understood, rather than expressed. In the following sentences, the nouns which are understood are enclosed in square brackets.
e.g. I have two pens. One is green and the other [pen] is blue.
One of my parents is a teacher; the other [parent] is a doctor.

Others is a pronoun. Others can be used to take the place of the word other, followed by a plural countable noun.
e.g. Those trees are hemlocks; the others are pines.
Ten people belong to the group, and five others are planning to join.
In the first example, others takes the place of the words other trees. In the second example, others takes the place of the words other people.

Others is often used in the expression some … others.
e.g. Some books are easy to read, but others are quite difficult.
Some people like classical music, while others prefer jazz.

The word else has a meaning similar to other. However, rather than being used as an adjective preceding a noun, else usually follows interrogative pronouns such as who and what, and indefinite pronouns such as anyone and someone.
e.g. Who else was at the meeting?
What else is on the agenda?
Has anyone else solved the problem?
Someone else may be able to help you.