How is data represented? - Data formats
The ISA supports several data formats by providing representations for integers, characters, floating-point, multimedia, etc.
Integer data formats can be signed or unsigned (e.g., in DEC Alpha there is byte, 16-bit word, 32-bit longword, and 64-bit quadword).
There are two ways of ordering byte addresses within a word
- big-endian: most significant byte first, and
- little-endian: least significant byte first.
There are also packed and unpacked BCD numbers, and ASCII characters.
Floating-point data formats (ANSI/IEEE 754-1985):standard, basic or extended, each having two widths: single or double.
Multimedia data formats are 32-, 64-, and 128-bit words (soon perhaps also 256-bit) concluding several 8- or 16-bit pixel representations or 32-bit (single precision) floating-point numbers used for 3D graphics.