🚀 go-pugleaf

In article <54...@bu.edu.bu.edu> a...@cs.bu.edu (Al Thompson) writes:
>In article <54...@bbn.COM> le...@BBN.COM (Joel B Levin) writes:
>|In article <ENTROPY.90...@pawl22.pawl.rpi.edu> ent...@pawl22.pawl.rpi.edu (Angel of Dope) writes:
>||In article <23...@tellab5.tellabs.com> to...@tellab5.tellabs.com (Joseph G. Toth Jr.) writes:
>||>   My WAG is that close to 98% of all op-codes available in
>||>   assemblers that generate machine code are 3 characters.
>||Oh my.  IBM 370 assembly language has mnemonics with lengths
>||between 1 (N, A, et al.) and 5 (STCTL et al.) and has had
>||such for a very long time indeed.  You microcomputer people
>||are all the same. 
>|
>|Oh, right.  370 indeed (not even 360!).
>|
>|Go back to 1401 Autocoder.  Or PDP-1 assembler.  I expect that very
>|few assemblers had strictly three character op-codes, but some of the
>|really old ones may have.
>
>Time out!  The opcode is a number, the letters are a mnemonic device so
>the programmer can avoid remembering the number.  There is no necessary
>correlation between the number of letters in the mnemonic and the number
>it represents.

Yes, however, due to memory limits, many of the assemblers were written
such that 3-bytes for the op-code with the 4th byte containing some data
on how to build that instruction.  It made the search/parse code really
simple.  (My PDP-11 assembler had that until Macro-11 came out and was
just tons better and needed a disk drive to work at reasonable rates)

/----------------------------------------------------------------------\
|      /// Michael Sinz -- CATS/Amiga Software Engineer                |
|     ///  PHONE 215-431-9422  UUCP ( uunet | rutgers ) !cbmvax!mks    |
|    ///                                                               |
|\\\///          "I don't think so," said Ren'e Descartes.             |
| \XX/                    Just then, he vanished.                      |
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