Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Path: utzoo!mnetor!uunet!seismo!mcvax!enea!diab!pf From: pf@diab.UUCP (Per Fogelstrom) Newsgroups: comp.arch Subject: Re: *Why* do modern machines mostly have 8-bit bytes? Message-ID: <239@diab.UUCP> Date: Fri, 24-Jul-87 03:45:26 EDT Article-I.D.: diab.239 Posted: Fri Jul 24 03:45:26 1987 Date-Received: Sat, 25-Jul-87 18:06:37 EDT References: <142700010@tiger.UUCP> <2792@phri.UUCP> <8315@utzoo.UUCP> <2807@phri.UUCP> <4957@milano.UUCP> Reply-To: pf@.UUCP (Per Fogelstrom) Organization: Diab Data AB, Taby, Sweden Lines: 13 Summary: Use power of two for anything larger than the smallest object. WHY 8-bit bytes.. The smallest ammount of data modern machines can deal with is a bit, and to simplify address computation it is best if the next larger addressable objects size is of any power of two size above. Take for example the trivial task to compute the address to the n'th element in an array. So an 8 bit "byte" (eight bits is a byte, aint it) is a power of two size object that is larger than a bit. (Imagine bit processing with a machine having 12 bit words. (using mod/div instead of and/shift).) But, on the other hand take a graphic engine with 24 bits as the smallest addessable object (8 bits each for red,green and blue). So all object sizes is "right" in their own context but for general processing, power of two's are most suitable. (I think.) per