6 Mar
2025
6 Mar
'25
5:28 a.m.
I thought Dennis said he didn’t the work on the 635 but you’re right, C was mostly on the
Pdp-11 and then targeted back to the 635.
Please consider the environment before reading this message.
John Levine, johnl(a)taugh.com
On Mar 5, 2025, at 23:36, Dan Cross
<crossd(a)gmail.com> wrote:
On Wed, Mar 5, 2025 at 11:11 PM John Levine <johnl(a)taugh.com> wrote:
This is a startling claim that I have never heard before. Can you cite
a source for this?
The history as recounted in Dennis Ritchie's paper on the history of C
(https://www.nokia.com/bell-labs/about/dennis-m-ritchie/chist.pdf) is
that the initial bootstrapping of PDP-7 Unix was done by
cross-assembling on a GE-635, with paper-tape hand carried to the PDP.
B appears to have been an invention that began life on the PDP-7 and
was subsequently ported to the PDP-11. But C did not appear until they
were solidly on the PDP-11, and was developed on that machine. The
earliest connections to other machines were Dennis Ritchie
constructing a cross-compiler for B that ran on the PDP-7; as he
described it:
|The most ambitious enterprise I undertook was a genuine cross-compiler
|that translated B to GE-635 machine instructions, not threaded code. It was
|a small tour de force: a full B compiler, written in its own language and
|generating code for a 36-bit mainframe, that ran on an 18-bit machine with
|4K words of user address space.
C was later ported to GE-635 and IBM 370, but there's no indication
it was created on the GE-635.
- Dan C
snip
And as for C: It was born on a 16-bit word system that expected 16-bit
aligned words, replacing B, a language with just the word datatype, on
a system with a 32KB (or less) user space, by people who had just come
from a project where waiting for working production PL/I compiler had
been a major headache, and generally suffered from "second system
syndrome" bloat.
I believe the earliest versions of C were on a GE 635, a word addressed
machine comparable to a PDP-10. But it moved to a PDP-11 soon enough
where the byte and word addresses motivated the datatypes that turned
B into C.