From mboxrd@z Thu Jan 1 00:00:00 1970 From: grog@lemis.com (Greg 'groggy' Lehey) Date: Tue, 15 Aug 2017 13:57:51 +1000 Subject: [TUHS] origin of string.h and ctype.h In-Reply-To: <09B7C59A-E3D4-4EA1-8DBE-794110D1CEBE@mcjones.org> References: <2ECAA475-891E-45D0-A354-B0B17284C138@mcjones.org> <09B7C59A-E3D4-4EA1-8DBE-794110D1CEBE@mcjones.org> Message-ID: <20170815035751.GC20775@eureka.lemis.com> On Monday, 14 August 2017 at 10:16:57 -0700, Paul McJones wrote: >> On Aug 14, 2017, at 9:09 AM, Paul Winalski wrote: >> >>>> ... >> >> The FORTRAN II arithmetic IF, with its three-way branch, was probably >> introduced to facilitate use of the conditional branch instructions of >> the IBM 704, which test the value of the accumulator and take a branch >> accordingly: >> >> TMI (transfer on minus) >> TMP (transfer on plus) My reference says TPL. >> TZE (transfer on zero) >> TNZ (transfer on not zero) >> >> It takes at most two of these instructions to implement the arithmetic IF. > > And the 709 added CAS (compare accumulator with storage): it skips > 0, 1, or 2 instructions depending on whether the contents of the > accumulator are algebraically greater, equal, or less than the > contents of the referenced memory location. It was my understanding that the 704 had this instruction too, and that it was almost certainly the background for arithmetic IF. Unfortunately, no reference I can find can confirm or deny this supposition. Another one is http://www.quadibloc.com/comp/cp0309.htm, which compares the instruction sets, but it's not categorical enough for my liking. But if I interpret it correctly, CAS was implemented on the 704. Do you see a proof of the contrary? In passing, my document also mentions the Honeywell 516, better known to Unix people as IMP. It, too, had a CAS-like instruction. Greg -- Sent from my desktop computer. Finger grog at lemis.com for PGP public key. See complete headers for address and phone numbers. This message is digitally signed. If your Microsoft mail program reports problems, please read http://lemis.com/broken-MUA -------------- next part -------------- A non-text attachment was scrubbed... Name: signature.asc Type: application/pgp-signature Size: 163 bytes Desc: not available URL: