Pascal not considered harmful - was Re: Rich kids are into COBOL

ben bfranchuk at
Fri Feb 20 18:44:29 CST 2015

On 2/20/2015 5:02 PM, Dave G4UGM wrote:

> Almost all , so there exceptions,  modern compliers are written in a high
> level language. Most use LEXX and YACC or their modern equivalents to
> generate the program fragments needed to generate the code.

I would say that is 50%. If you have LEXX and YACC you tend have a
UNIX system with a C compiler.

>> You have a front-end, which does the lexical work and translates the
>> program into some intermediate form, such as a tree.  In the middle, you
>> have optimization and checking--and finally, you have the back end which
>> essentially emits code--but that doesn't necessarily imply that the
> compiler
>> author knows the numeric opcodes or the  precise instruction format.  Many
>> compiler backends feed into an existing assembler, which puts it all
> together.

How do handle byte operations in C like *x++ on a PDP 10?

>> Knowing the numeric opcodes and instruction format isn't all that it would
>> seem to be.  I never had much more than a passing familiarity with the
>> numeric opcodes of the CDC STAR--given that there was 8 bits for the
>> opcode and 8 more "modifier" bits, you arguably had a machine with
>> thousands of opcodes.  What was hardest and very important was
>> committing to memory the *timings* of those instructions, within a
>> superscalar, segmented, pipelined vector architecture.

Time for POWER code re-arrangement.

>> --Chuck

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