Real Origin of the DECUS C Compiler?

Joerg Micheel joerg at
Wed Mar 18 12:58:21 AEST 1998

# In article by Ken Wellsch:
# > I wasn't aware the DECUS C compiler (written in assembler) took anything
# > from V6 and/or V7 but I may well be wrong.  The DECUS C stuff had a
# > special interest to me back in the Waterloo days because I believe
# > a former U of Waterloo person wrote it long ago...
# Hmm, that's what I'd heard. Perhaps the person who told me this was wrong.
# Can anybody tell us the correct origins of the DECUS C compiler?

One thing I can tell for sure: the DECUS C Compiler and the K&R CC are
completely different in their origins. I'm about 90% sure the DECUS XCC
is written in MACRO-11.

The reason I'm so sure is because we were looking at a suitable C compiler
to run on our 11/34 back in 1989 and we first mungled with the DECUS XCC.
But this one had several deficiencies, among them I remember lack of blocks
within functions, local variable initialization, difficulties with typedefs/structs.
Maybe, Harti could tell more.

We were looking into Johnson's pcc, but this one turned out to be a too big
piece of work and to slow to run on our 128 KWord machine.

Harti tried to port the Whitesmith CC from RT11, and it ran, but there were
deficiencies with the RT emulation, so we dropped that.

Finally, we took the K&R UNIX CC and reworked it so that it would pass the
DECUS XCC to produce the stage one. We wrote our own unix assembler supporting
the RSX object file format from scratch. Later, we recompiled the K&R CC on
RSX with itself. This system became our workhorse for the next 2 years, the
compiler is still amazingly fast, both in terms of runtime and the code being
produced. (Quoted: Harti)

So here are the 4 different original sources of C compilers for the 11, though,
admittedly, 2 of them would run on DEC's original OS, not on UNIX, which I guess,
makes them somewhat irrelevant to PUPS. Am I right here ? (Where do we draw the
boundary ?)


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