Definition
A base-16 numbering system used in digital electronics and computing, in which each digit represents a value from 0 to 15. The digits 0 through 9 represent their normal values, and the letters A through F represent the values 10 through 15. Hexadecimal is commonly used to express binary data in a more compact, human-readable form, since each hex digit corresponds exactly to four binary digits (bits).
Plain English
A counting system that uses 16 symbols instead of the usual 10. After 9, it keeps going with A, B, C, D, E, and F before rolling over. It's a shorthand way of writing long strings of 1s and 0s used inside computers and avionics.
Context Anchor
Seen in avionics, digital equipment manuals, software settings, fault codes, memory addresses, and electronic maintenance information.
Derivation
From the Greek 'hex' meaning six and the Latin 'decimal' meaning based on ten — together, 'sixteen.' The name simply tells you the system counts in groups of sixteen rather than ten.
Why Pilots Care
Pilots rarely use hexadecimal directly, but technicians and avionics troubleshooters do. Fault codes displayed on flight management systems, GPS units, or engine monitors are often shown in hex, and recognizing the format helps when reading maintenance reports or relaying codes to a shop.
Analogy
Think of it like a counting system with sixteen digits instead of ten. In normal counting, after 9 you write 10; in hexadecimal, after 9 you count A, B, C, D, E, F, and then write 10.
Intuition Check
Do not assume the letters in a hexadecimal number are words or abbreviations. In this system, A through F are number symbols.
Example Sentence 1
The avionics technician read the fault code 0x2F from the flight computer's diagnostic page, which is hexadecimal for the decimal number 47.
Example Sentence 2
Some aircraft diagnostic tools display error codes in the hexadecimal number system for precise identification.