The name of 16 and 32 bits

Question

8 bits is called "byte". How is 16 bits called? "Short"? "Word"?

And what about 32 bits? I know "int" is CPU-dependent, I'm interested in universally applicable names.

Answer 1

The correct name for a group of exactly 8 bits is really an octet. A byte may have more than or fewer than 8 bits (although this is relatively rare).

Beyond this there are no rigorously well-defined terms for 16 bits, 32 bits, etc, as far as I know.

Answer 2

A byte is the smallest unit of data that a computer can work with. The C language defines char to be one "byte" and has CHAR_BIT bits. On most systems this is 8 bits.

A word on the other hand, is usually the size of values typically handled by the CPU. Most of the time, this is the size of the general-purpose registers. The problem with this definition, is it doesn't age well.

For example, the MS Windows WORD datatype was defined back in the early days, when 16-bit CPUs were the norm. When 32-bit CPUs came around, the definition stayed, and a 32-bit integer became a DWORD. And now we have 64-bit QWORDs.

Far from "universal", but here are several different takes on the matter:

Windows:

• BYTE - 8 bits, unsigned
• WORD - 16 bits, unsigned
• DWORD - 32 bits, unsigned
• QWORD - 64 bits, unsigned

GDB:

• Byte
• Halfword (two bytes).
• Word (four bytes).
• Giant words (eight bytes).

<stdint.h>:

• uint8_t - 8 bits, unsigned
• uint16_t - 16 bits, unsigned
• uint32_t - 32 bits, unsigned
• uint64_t - 64 bits, unsigned
• uintptr_t - pointer-sized integer, unsigned

(Signed types exist as well.)

If you're trying to write portable code that relies upon the size of a particular data type (e.g. you're implementing a network protocol), always use <stdint.h>.