GCSE Computer Science (WJEC)

Topic Summaries

COMPUTER SYSTEMS: Number systems

Converting denary and hexadecimal

  • Hexadecimal is base-16, using digits 0–9 and letters A–F.
  • 1 hex digit = 4 binary bits.
  • For example: 255 in denary = FF in hex.
Denary 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Hex 0 1 2 3 4 5 6 7 8 9 A B C D E F
  • To convert hexadecimal to binary: multiply the value of the first digit by 16, then add the second digit (e.g. D4 → D = 13 → 13 × 16 = 208 208 + 4 = 212).
  • To convert denary into hexadecimal: divide the number by 16 and use the integer as the first digit and the remainder as the second (e.g. 179 → 176/16 = 11.3 → 11 = B → first digit B, second digit 3 → B3).

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