Data Representation & Storage

Everything a computer stores is ultimately binary. This outcome covers how numbers, characters and larger structures are represented, and how much space they take.

Data: Raw, unprocessed facts — 78, 'Ayanda', 2026-03-15.
Information: Data processed into something meaningful — 'Ayanda's average is 78%'.
Knowledge: Information applied to make a decision — 'Ayanda qualifies for the top class'.

Unit	Size	Note
Bit	A single 0 or 1	The smallest unit
Nibble	4 bits	Exactly one hexadecimal digit
Byte	8 bits	One ASCII character; 256 possible values
KB / MB / GB / TB	×1 000 each (decimal)	Manufacturers use 1 000; RAM is quoted in powers of 1 024

Three number systems appear in the exam: decimal (base 10), binary (base 2) and hexadecimal (base 16). Hex is a shorthand for binary — one hex digit is exactly four bits, which is why colour codes and memory addresses use it.

Example

Decimal 45 to binary: 45 ÷ 2 = 22 r 1 (least significant bit) 22 ÷ 2 = 11 r 0 11 ÷ 2 = 5 r 1 5 ÷ 2 = 2 r 1 2 ÷ 2 = 1 r 0 1 ÷ 2 = 0 r 1 (most significant bit) Read the remainders upwards: 101101 Check: 32 + 8 + 4 + 1 = 45 ✓ Binary 101101 to hex: group in fours from the right 0010 1101 -> 2 D -> 2D

Type	Typical size	Holds
Integer	4 bytes	-2 147 483 648 to 2 147 483 647
Real / Double	8 bytes	Fractional values, with rounding error
Char	1-2 bytes	One character
Boolean	1 byte	True or False
String	1 byte per char + overhead	Text of any length

ASCII: 1 byte per character, 128 standard codes. 'A' = 65, 'a' = 97, '0' = 48 — worth memorising.
Unicode / UTF-8: Extends ASCII to every writing system. UTF-8 uses 1-4 bytes and is backwards-compatible with ASCII.
Lossy vs lossless: Lossy compression (JPEG, MP3) discards data permanently; lossless (PNG, ZIP) restores the original exactly.

💡 Exam Tip

'a' - 'A' = 32 in ASCII, which is why adding or subtracting 32 converts case. Exam questions love this.