Computer Science • Number Systems

Hexa-Tac

4-bit: one hex digit

  • Green aliens carry binary, in nibbles (1011)
  • Blue aliens carry denary
  • A shot that matches nothing, or an enemy that lands, costs a life. You have 5.
Your best in this mode: 0

Hexa-Tac — Explanation

Enemies fall from orbit, each carrying a number: green aliens carry it in binary, blue aliens in denary. Shoot one down by typing the same number in hexadecimal before it reaches the ground.

Type with the keys 0–9 and A–F, or tap the keypad under the game. A shot always goes to the lowest enemy with that number. A shot that matches nothing on screen costs a life, and so does an enemy that reaches the ground: you start with 5. The longer you last, the faster and more often they come.

Converting quickly

Each hex digit stands for exactly four bits (a nibble), which is why binary codes are shown split into fours. Convert each nibble on its own: 1011 0101 is 1011 = 11 = B and 0101 = 5, so B5.

For denary, divide by 16: the whole number is the first hex digit and the remainder the second. 181 ÷ 16 = 11 remainder 5, so 181 is B5 too. Digits above 9 are letters: A = 10, B = 11, C = 12, D = 13, E = 14, F = 15.

Objective: convert between binary, denary and hexadecimal quickly and accurately, recognising the hexadecimal for a 4-bit or 8-bit binary value, or a denary value from 0 to 255, on sight (for example, Cambridge IGCSE Computer Science 0478, 1.1 number systems; 9618, 1.1 data representation).

Where this fits

  • AQA: AQA A Level Computer Science (7517)
  • Cambridge: Cambridge IGCSE Computer Science (0478); Cambridge A Level Computer Science (9618); Cambridge AS Level Computer Science (9618)
  • IB: IB Computer Science HL; IB Computer Science SL
  • Pearson Edexcel International: Edexcel International GCSE Computer Science (4CP0)
  • USDP: USDP Computer Science

Hexa-Tac — Key Terms

Key concepts in English, with te reo Māori, Chinese (Simplified) and Korean.

EnglishTe reo Māori中文（简体）한국어What it means on this page
Binarytāhūrua二进制이진법A number system using only two digits, 0 and 1 — how every value is actually stored inside a computer.
Denarypūnaha tekau十进制십진법The ordinary base-10 number system people count in day to day. Also called decimal.
Hexadecimalno attested term十六进制십육진법A base-16 number system (digits 0–9 then A–F) used as a compact, human-readable stand-in for binary.
Bitmoka位비트A single binary digit — a 0 or a 1.
Nibbleno attested term半字节니블4 bits — exactly the range a single hex digit can represent (0–F).
Bytepaita字节바이트8 bits — exactly the range two hex digits can represent (00–FF).
Most significant bitno attested term最高有效位최상位 비트The left-most bit in a binary value — the one worth the most.
Basepūtake进制진법How many distinct digits a number system uses before it carries over — 2 for binary, 10 for denary, 16 for hexadecimal.

On the te reo Māori column. Terms marked as gaps have no attested equivalent in the sources checked — Karaitiana Taiuru's Dictionary of Māori Computer and Social Media Terms, Paekupu, the Reserve Bank's te reo financial glossary, NZQA and Te Aka. No coinage is printed as though it were established; where a class needs one, commission it from Te Taura Whiri i te Reo Māori and credit the translator. Te reo Māori is not italicised and takes no plural "s".