Computer Science - 9210 OxfordAQA

Character Encoding

Gbogbo ọrọ náà

Memory holds numbers. Text is not numbers. Somewhere between the key you press and the letter that appears there has to be an agreement, written down and obeyed by every piece of hardware and software in the chain, that this particular pattern of bits means the letter H. That agreement is a character set, and the whole reason you can send a message from a phone in one country to a laptop in another and have it arrive readable is that both ends are using the same one.

This lesson covers the two encoding methods the specification names, 7-bit ASCII and Unicode. You will learn what a character set actually is, why the codes inside one are arranged in runs rather than scattered, how to use a given table to go from characters to codes and back, and why a scheme with only 128 codes could not serve a world that writes in hundreds of scripts. You will also meet the single most useful consequence of the sequential arrangement: once you know one code in a group, you can work out the rest by counting.

Ebumnobi

  1. Understand what a character set is and be able to describe the following character encoding methods:
  2. 7-bit ASCII
  3. Unicode. Understand that character codes are commonly grouped and run in sequence within encoding tables.
  4. Describe the purpose of Unicode and the advantages of Unicode over ASCII.
  5. Know that Unicode uses the same codes as ASCII up to 127.

Maapụ uche

E seela isiokwu a ka ị hụ otu echiche si ejikọta.

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Akwụkwọ Ọmụmụ

Suppose you and a friend decide to pass notes in a code where 1 means A, 2 means B and so on. The code works, but only because you both wrote the same list down beforehand. If your friend had numbered the alphabet backwards, every message you sent would arrive as nonsense, and nothing in the numbers themselves would tell either of you which of you was wrong.

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Nnyocha Ọmụmụ

Ekele diri gi maka imecha ihe karịrị na Character Encoding. Ugbu a na ị na-enyochakwa isi echiche na echiche ndị dị mkpa, ọ bụ oge iji nwalee ihe ị ma. Ngwa a na-enye ụdị ajụjụ ọmụmụ dị iche iche emebere iji kwado nghọta gị wee nyere gị aka ịmata otú ị ghọtara ihe ndị a kụziri.

Ị ga-ahụ ngwakọta nke ụdị ajụjụ dị iche iche, gụnyere ajụjụ chọrọ ịhọrọ otu n’ime ọtụtụ azịza, ajụjụ chọrọ mkpirisi azịza, na ajụjụ ede ede. A na-arụpụta ajụjụ ọ bụla nke ọma iji nwalee akụkụ dị iche iche nke ihe ọmụma gị na nkà nke ịtụgharị uche.

Jiri akụkụ a nke nyocha ka ohere iji kụziere ihe ị matara banyere isiokwu ahụ ma chọpụta ebe ọ bụla ị nwere ike ịchọ ọmụmụ ihe ọzọ. Ekwela ka nsogbu ọ bụla ị na-eche ihu mee ka ị daa mba; kama, lee ha anya dị ka ohere maka ịzụlite onwe gị na imeziwanye.

  1. How many different characters can be represented using 7-bit ASCII? A. 7 B. 64 C. 128 D. 256 Answer: C
  2. In ASCII the character A has the code 65. What is the character code for D? A. 66 B. 67 C. 68 D. 69 Answer: C
  3. Which statement about Unicode is correct? A. Unicode can represent fewer characters than ASCII B. Unicode uses the same codes as ASCII up to 127 C. Unicode uses exactly 7 bits for every character D. Unicode cannot represent the English alphabet Answer: B
  4. The character codes for the lower case letters begin with a at 97. What is the code for the letter d? A. 99 B. 100 C. 101 D. 104 Answer: B
  5. Why are the character codes for the capital letters stored in sequence? A. So that the codes for the rest can be worked out once one is known B. So that capital letters take up less memory than lower case letters C. So that the codes can be stored without using any bits D. So that the same code can mean two different characters Answer: A

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Ị chọrọ ime ajụjụ ule ọmarịcha gbasara Character Encoding? Budata ngwa Green Bridge CBT iji nweta ajụjụ ule ọmarịcha na nyocha zuru ezu gbasara isiokwu a.

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