From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=unavailable autolearn_force=no version=3.4.4 Path: eternal-september.org!reader01.eternal-september.org!reader02.eternal-september.org!feeder.eternal-september.org!feeder4.usenet.farm!feed.usenet.farm!feeder.usenetexpress.com!feeder-in1.iad1.usenetexpress.com!border1.nntp.dca1.giganews.com!nntp.giganews.com!buffer1.nntp.dca1.giganews.com!nntp.earthlink.com!news.earthlink.com.POSTED!not-for-mail NNTP-Posting-Date: Sat, 23 Jun 2018 09:48:29 -0500 From: Dennis Lee Bieber Newsgroups: comp.lang.ada Subject: Re: Why are Ada compilers difficult to write ? Date: Sat, 23 Jun 2018 10:48:29 -0400 Organization: IISS Elusive Unicorn Message-ID: References: <98aac007-7512-4ae3-94de-f02e7e2651ae@googlegroups.com> <87k1qr8oyz.fsf@nightsong.com> <8e8e7ce9-d7ac-4ec5-8278-7b93cec46599@googlegroups.com> <145294063.551401932.678101.laguest-archeia.com@nntp.aioe.org> <300422673.551411179.249790.laguest-archeia.com@nntp.aioe.org> User-Agent: ForteAgent/8.00.32.1272 X-No-Archive: YES MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Usenet-Provider: http://www.giganews.com NNTP-Posting-Host: 76.255.154.65 X-Trace: sv3-xC3H+uaLxE8rF2PoAGsZt2K5iYo1T+wxnnoAJPz/aVQ5WBUW9KORf/4TGIGuBJ207fOydmvwq6NmfEg!vvAUO1lO3izVbsxsqOJrzJIJ7E9iLVPQa9Z2wgTcid7sIayXdl3MhN89ajvEKb7hMQwC7p4tz7u+!f/FugaiPlxtygJhtMwvrmhSMmQk= X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint properly X-Postfilter: 1.3.40 X-Original-Bytes: 2549 Xref: reader02.eternal-september.org comp.lang.ada:53269 Date: 2018-06-23T10:48:29-04:00 List-Id: On Fri, 22 Jun 2018 19:54:59 -0700 (PDT), "Dan'l Miller" declaimed the following: > >Yes, but the Z80 has the 8080's three 16-bit registers BC, DE, and HL by concatenating 8-bit register pairs, but the Z80 has three more shadow 16-bit registers BC', DE', and HL' that can be swapped in and out. (Plus AF and AF' if you like living dangerously with the flag registers.) 6502 needed the page-zero trick because its register-set was so spartan. (Only TI's TMS9900 had an even more spartan register-set in that era.) > As I recall, for all practical purposes, the 9900 did not have general purpose registers -- it had a "register pointer" into RAM (Just checked -- "Workspace Pointer" to 16 16-bit "registers" located in RAM). The other two "real" registers were the program counter and status. In essence, general purpose registers were indexed indirect addresses. -- Wulfraed Dennis Lee Bieber AF6VN wlfraed@ix.netcom.com HTTP://wlfraed.home.netcom.com/