NetNews Usenet Archive 1992 #26/NN_1992_26.iso/spool/comp/lang/c/16429

Internet Message Format | 1992-11-12 | 2.4 KB

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From: [e-mail] (Jamshid Afshar)
Newsgroups: comp.lang.c
Subject: Re: Typedefing builtin... thanks.
Message-ID: <[e-mail]>
Date: 12 Nov 92 22:13:10 GMT
References: <[e-mail]>
Reply-To: [e-mail]
Organization: The University of Texas at Austin; Austin, Texas
Lines: 40

In article <[e-mail]> [e-mail] (Jonatan Kutchinsky) writes:
>People generally tended to agree with me on the use of the names BYTE, WORD,
>and LWORD to represent unsigned 8, 16, and 32 bit variables in my simulation
>of a Motorola 68000 processor. Some even proposed the use of special
>functions or macros for calculations, conversions to builtin types, and for
>I/O. We are going to use this in our computer science project.

I agree, but remember these typedefs are only appropriate because that
is what your application is modeling.  It would use these typedefs as
another app would use HostID or SocialSecurityNumber.  The rest of
your code should use int, long, etc.  I agree it would be a good idea
to use functions/macros for performing the 68000 arithmetic operations
instead of just writing
    WORD r1, w1, w2;
    /*...*/
        r1 = w1 * w2;
especially since multiplication in the processor might result in a
LWORD (?), while in C the result is the same type as the operands.

>One stated that in his ideal program, builtin types were never used, and
>names like f.x. Counter, and BigCounter would represent int and perhaps long,
>depending on the machine used.

I don't agree with this at all.  That extra level of abstraction adds
nothing and introduces its own complications (eg, what type specifier
do you use for printf()?).

>The major arguments used to justify these techniques were about portability.
>A program is easier to port, when you can change some typedefs in a header
>file, instead of changing a lot of ints to longs all over the code.

I see your BYTE, WORD typedefs as increasing readability and providing
data abstraction, which eases porting.

In general you should not have to change your code from using 'int' to
using 'long'.  Use 'long' if the value might be larger than 16-bits,
otherwise just use 'int'.  Often you can use 'size_t'.

Jamshid Afshar
[e-mail]