From mboxrd@z Thu Jan 1 00:00:00 1970 To: 9fans@cse.psu.edu From: "Douglas A. Gwyn" Message-ID: <3C025AE5.308292A3@null.net> Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit References: <87n11f1t0i.fsf@becket.becket.net>, <3BFDDB2B.DC0423B3@null.net>, <87u1vlwcnc.fsf@becket.becket.net> Subject: Re: [9fans] on TCP vs IL Date: Mon, 26 Nov 2001 15:21:30 +0000 Topicbox-Message-UUID: 295ded90-eaca-11e9-9e20-41e7f4b1d025 "Thomas Bushnell, BSG" wrote: > ... Though, as I was once taught, a "byte" > is officially the minimal addressible unit on an architecture... No, although within C the term "byte" is practically synonymous with "minimum unit addresable by standard language constructs". Generally, a byte is a collection of bits within a machine word that are treated as representing a complete field. Some systems had variable-sized byte instructions, some had fixed-size byte operations, some had no direct support for bytes (although one could use word-oriented instructions to manipulate artificially defined byte fields). > But these days the philistines have forgotten about fine old 36-bit > wordsize machines and the like, and have just synonymized "byte" and > the neologism "octet". The 8-bit byte became common with 16-bit minicomputers and the IBM System/360. Consequently when storage devices for those platforms had their capacity specified in "bytes", everyone understood that to mean 8-bit bytes. This carried over into other processors, especially since the 8-bit byte sufficed for the most common character encodings of the time, ASCII and EBCDIC. But since "byte" does not logically always imply 8 bits, careful specifications such as the IETF Internet RFPs tend to use the term "octet" when exactly 8 bits are meant.