[TUHS] Algol68 vs. C at Bell Labs

[Brantley Coile]

Wirth attempted to write a simple language to write the real Pascal compiler. One fatal flaw was that the simpler language lacked recursion, which was optional in those days, and the use of the Pascal-0 was abandoned. The next attempt was to write the compiler in Pascal and ``desk’’ compile it into machine code. That was amazingly successful, if tedious.

Later, to make porting easier, the good professor wrote a version that generated a stack based intermediate code called P-code. You could get a copy of the compiler in Pascal and P-code, write your own P-code interpreter and have a Pascal compiler. It was easy. Pascal compilers spread like locus after that. One could then change the compiler to write machine code for the actual machine, although many just extended their P-code emulators. It was “compile once, run anywhere” long before Java’s virtual machine.

BCPL came the same way, with a version of the compiler in CINIT code to move the compiler. 

The PCC required a donor machine already running Unix in somewhat close proximity to the target machine.

  Brantley Coile

> On Jun 30, 2016, at 1:17 PM, Nelson H. F. Beebe <beebe at math.utah.edu> wrote:
> 
> Ori Idan <ori at helicontech.co.il> asks today:
> 
>>> Pascal compiler written in Pascal? how can I compile the compiler it I
>>> don't yet have a pascal compiler? :-)
> 
> You compile the code by hand into assembly language for the CDC
> 6400/6600 machines, and bootstrap that way: see
> 
> 	Urs Ammann
> 	On Code Generation in a PASCAL Compiler
> 	http://dx.doi.org/10.1002/spe.4380070311
> 
> 	Niklaus Wirth
> 	The Design of a PASCAL Compiler
> 	http://dx.doi.org/10.1002/spe.4380010403
> 
> It has been a long time since I read those articles in the journal
> Software --- Practice and Experience, but my recollection is that they
> wrote the compiler in a minimal subset of Pascal needed to do the job,
> just to ease the hand-translation process.
> 
> -------------------------------------------------------------------------------
> - Nelson H. F. Beebe                    Tel: +1 801 581 5254                  -
> - University of Utah                    FAX: +1 801 581 4148                  -
> - Department of Mathematics, 110 LCB    Internet e-mail: beebe at math.utah.edu  -
> - 155 S 1400 E RM 233                       beebe at acm.org  beebe at computer.org -
> - Salt Lake City, UT 84112-0090, USA    URL: http://www.math.utah.edu/~beebe/ -
> -------------------------------------------------------------------------------