Text, Sound and Images

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.