Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!cs.utexas.edu!sun-barr!ames!bionet!hayes.ims.alaska.edu!floyd
From: floyd@ims.alaska.edu (Floyd Davidson)
Newsgroups: comp.os.cpm
Subject: Re: System use of Z80 registers
Message-ID: <1990Dec4.131328.15594@ims.alaska.edu>
Date: 4 Dec 90 13:13:28 GMT
References: <9011261759.AA10916@newton> <6209@balu.UUCP>
Organization: University of Alaska, Institute of Marine Science
Lines: 32

In article <6209@balu.UUCP> tilmann@cosmo.UUCP (Tilmann Reh) writes:
>Bridger Mitchell writes:
>>   SYSTEM CODE (BIOS, BDOS, INTERRUPT-SERVICE ROUTINES, AND BACKGROUND
>>   UTILITIES)  SHOULD *ALWAYS PRESERVE* THE NON-8080 REGISTERS.
>>				 ****
>>
>> This rule ensures that an application that uses Z80 opcodes can run on
>> any z80 system without having to save and restore any of those
>> registers before every BIOS and BDOS call.
>
>That's a guideline I don't agree with.
>Why should the system care about which registers the application program uses?
>The responsibility for register contents is *only* at the application
[...]
>
>When will programmers (system *and* application) finally understand that
>everything should be programmed as portable and universal as possible ?
>

You're last statement does not follow from the first.  For maximum
portability both should assume the other did it wrong.  Both
applications programmer and system programmer should protect the
registers.  I think the performance cost is small if a little
thought is given to register use.

Floyd


-- 
Floyd L. Davidson                             floyd@hayes.ims.alaska.edu
Salcha, AK 99714                    paycheck connection to Alascom, Inc.
 When I speak for them, one of us will be *out* of business in a hurry.