On 1/29/21 11:40 AM, Nemo Nusquam via cctalk wrote: > On 29/01/2021 14:20, Fred Cisin via cctalk wrote: >> We don't need another BIG-endian/little-endian debate! >> (when a 16 bit number is stored in bytes, does the high order byte >> come first, or the low order byte?) (cf. intel V Motorola) > Amen to that (but did it not originate with DEC vs. IBM?) > > N.
It was the result of sub-word addressable architecures. Most old (pre S/360) digit/character-addressable architectures were big-endian (i.e. higher-order characters occupied lower addresses) Even PDP-11 isn't strictly little-endian, though Intel X86 definitely is. Numbering of bits in a word is also interesting. Is the high order bit in a 64 bit word, bit 0 or bit 63? Both conventions have been employed. This really gets interesting on bit-addressable architectures. STAR for example, is bit addressable, but big-endian, with alignment of data dependent on the data type (e.g. bytes must have the lower 3 bits of their address as 000; halfwords as 00000 and so on. However, it's possible to extract any group of bits from a bit-addressed datum. --Chuck --Chuck
