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From: mouse@mcgill-vision.UUCP (der Mouse)
Newsgroups: comp.arch
Subject: Re: bit, byte, and word level addressing
Message-ID: <744@mcgill-vision.UUCP>
Date: Sun, 26-Apr-87 14:43:35 EDT
Article-I.D.: mcgill-v.744
Posted: Sun Apr 26 14:43:35 1987
Date-Received: Sun, 3-May-87 18:39:42 EDT
References: <16038@amdcad.AMD.COM> <1239@ames.UUCP> <466@alliant.UUCP>
Distribution: world
Organization: McGill University, Montreal
Lines: 26
Keywords: word alignment, bit level addressing, memory accesses

In article <466@alliant.UUCP>, steckel@alliant.UUCP (Geoff Steckel) writes:
> C is/was unable to deal with bit arrays because the PDP11 didn't have
> bit pointers.  I would be very curious to hear how many
> programs/programmers would _use_ bit fields & bit arrays on a regular
> basis if they were easier to use.

I certainly would.  I regularly waste 87.5% of the space in some arrays
because I need only a boolean but I can't have an array of single bits
without great pain, while memory is cheap.  Of course, if the
difference is a lot of memory, I will go to bit arrays (eg, mark bits
for a lisp garbage collector I implemented - need one per datum, datum
can be as small as 8 bytes; using one byte to mark eight seemed
excessive).

> This leads me to formulate a rule:  any data type not easily
> addressed is a 'second-class datatype' and will be avoided by
> programmers.  Any agreement or disagreement?

Strong agreement.  I even find myself avoiding long and short integers
because their names are 5 and 6 characters (respectively) longer than
simple integers.  (Yes, I know this is not a teriffically good practice
and will probably bite me someday.)

					der Mouse

				(mouse@mcgill-vision.uucp)