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0984

Text, Sound and Images

Data Representation · 3 question types

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0984 Topics

Number Systems12%
Text, Sound and Images5%
  1. Character Sets
  2. ASCII
  3. Unicode
  4. ASCII vs Unicode Comparison
  5. How Sound Is Represented
  6. Sound File-Size Calculations
  7. How Images Are Represented (Bitmaps)
  8. Image File-Size Calculations
Data Storage and Compression4%

Frequency legend

High (≥14%)
Above avg (10 to 13%)
Average (<10%)

Exam Frequency Analysis

Past paper frequency (2018 to 2024)

This topic accounts for approximately 5% of your exam marks.

stable
Rare
Stable5%

ASCII/Unicode, sound sampling and pixel/colour depth appear regularly as 2 to 4 mark questions.

Every computer stores text as patterns of binary digits. A character set is the agreed table that maps each character (a letter, a digit, a punctuation mark, an emoji) to a unique binary code. Without a shared character set, a binary value like 01000001 might be interpreted as the letter A on one machine and as a different symbol on another.

A few key ideas about character sets:

  • Each character has a unique binary code. No two characters share the same code.
  • The codes follow a logical sequence. Consecutive letters (A, B, C) and consecutive digits (0, 1, 2) get consecutive numbers, so the difference between any two adjacent characters is always 1.
  • The number of bits decides how many characters can be represented. With n bits there are 2ⁿ possible codes.

The two character sets you must know for the exam are ASCII and Unicode.

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ASCII