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From: EGC4MV2@UCLAMVS.BITNET (2 Michael Van Norman)
Newsgroups: comp.lang.asm370
Subject: Re: Re: why code in 370 Assembler
Message-ID: <9104241700.AA04584@ucbvax.Berkeley.EDU>
Date: 24 Apr 91 16:55:00 GMT
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Reply-To: IBM 370 Assembly Programming Discussion List
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> I think the point about the MVC instructions is being missed. The point is
> that to copy a fixed length character string (assuming that all definitions
> are properly made), then:
>     MVC   TO,FROM          in BAL is clear
>     TO = FROM;             in various HLL's is clearer and machine independent
>     memcpy(TO,FROM,sizeof(TO)); in C is very ugly and hard to read

On the contrary I find this very easy to read.  In fact the memcpy
statement is no different from the MVC statement except for the addition
of the length parameter.  The only real addition is the parenthesis.
Take the ()'s out and you have  MVC    TO,FROM
                                memcpy TO,FROM,LENGTH
This looks the same to me :)

As for TO = FROM, if the memory to be copied is a structure the
TO = FROM will work in ANSI C.

> The C compiler may generate a single MVC, but it's harder to write and read
> then assembler in this case. Many other things in C require jumping thru
> hoops to accomplish simple tasks and therefore make programs hard to read.

You could always just #define MVC(x,y) memcpy(x,y,sizeof(x))

Then you could write MVC(TO,FROM) all you want!

Michael Van Norman                     11334 University Research Library
Programmer/Analyst                     405 Hilgard Avenue
Library Administrative Computing       Los Angeles, CA  90024-1575
EGC4MVN@mvs.oac.ucla.edu               (213)825-1206