Computer Science - 4CP0 PearsonEdexcel

Data Representation

Gbogbo ọrọ náà

A photograph, a song and a paragraph of text look nothing alike, yet a computer stores all three the same way: as binary digits. The difference is entirely in how those digits are agreed to be interpreted, letter by letter for text, pixel by pixel for an image, sample by sample for sound.

In this lesson you will learn how characters are encoded using ASCII and Unicode, how a bitmap image's resolution and colour depth determine its uncompressed file size, how an analogue sound wave is converted into binary using sampling, and why the number of bits available always limits how faithful any of these digital representations can be.

Ebumnobi

  1. Understand how computers encode characters using ASCII and Unicode
  2. Understand how bitmap images are represented in binary (pixels, resolution, colour depth)
  3. Understand how sound, an analogue signal, is represented in binary
  4. Understand the limitations of binary representation of data (sampling frequency, resolution) when constructed by the number of available bits

Akọmọ Ojú-ẹkọ

A computer has no built-in idea of what a letter is. To store text, every character a keyboard can produce is given its own unique binary number, called a character code. ASCII (American Standard Code for Information Interchange) does this using 7 bits, giving 128 possible codes, enough for the upper- and lower-case English alphabet, digits, punctuation and basic control characters. An 8-bit version, extended ASCII, adds a further 128 codes for accented letters and symbols.

Ọ dị na ngwa Green Bridge

Budata ngwa Green Bridge CBT na ekwentị maọbụ kọmputa gị iji nweta akwụkwọ ndụmọdụ zuru oke, ajụjụ mmụta, na ndị ọzọ.

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Ayẹwo Ẹkọ

Ekele diri gi maka imecha ihe karịrị na Data Representation. 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. The upper-case letter 'A' has the ASCII code 65. What is the ASCII code of the lower-case letter 'a'? A) 33 B) 66 C) 97 D) 129 Answer: C
  2. An image is 100 pixels wide, 50 pixels tall, and uses a colour depth of 8 bits. What is its uncompressed file size in bits? A) 4 000 B) 8 000 C) 40 000 D) 400 000 Answer: C
  3. Which setting controls how many amplitude levels a single digital audio sample can be stored as? A) Sample rate B) Bit depth C) Number of channels D) File format Answer: B
  4. A recording is made with too low a sample rate. What is the most likely effect on the digital recording? A) The file becomes larger than expected B) Rapid changes in the original sound are missed C) The recording gains extra colour depth D) The recording becomes louder Answer: B
  5. What is the main reason Unicode was developed alongside ASCII? A) To make text files smaller B) To represent far more characters than ASCII can, covering the world's writing systems and symbols C) To replace binary with a new number system D) To increase a computer's sample rate Answer: B

Ọ dị na ngwa Green Bridge

Budata ngwa Green Bridge CBT na ekwentị maọbụ kọmputa gị iji nweta akwụkwọ ndụmọdụ zuru oke, ajụjụ mmụta, na ndị ọzọ.

Akwụkwọ ndụmọdụ zuru oke nwere eserese
Onye inyeaka mmụta AI
Mụọ n'ụzọ na-enweghị ịntaneti, oge ọbụla, ebe ọbụla
Ọ dị na Android, Windows, macOS, na Linux

Ọ dị na ngwa Green Bridge

Budata ngwa Green Bridge CBT na ekwentị maọbụ kọmputa gị iji nweta akwụkwọ ndụmọdụ zuru oke, ajụjụ mmụta, na ndị ọzọ.

Akwụkwọ ndụmọdụ zuru oke nwere eserese
Onye inyeaka mmụta AI
Mụọ n'ụzọ na-enweghị ịntaneti, oge ọbụla, ebe ọbụla
Ọ dị na Android, Windows, macOS, na Linux

Meecha Ajụjụ Ule Ọmarịcha

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

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