|Computer||English Electric KDF 9|
English Electric Leo Marconi Computers
|Owned by|| English
Electric Ltd - Stafford
| At the end of
1967 I got restless again and I joined English Electric in Stafford as
part of a team to plan for a new computer system (see System 4) to
replace their KDF9. The first thing I did was to be trained on the KDF9
at the English Electric Computers site at Kidsgrove (north of Stoke).
However I would never program it for real.
|Programming|| KDF9 assembler
was a strange language( "The
KDF9 is remarkable because it is
to have been the first zero-address instruction format computer to have
been announced (in 1960). It was first delivered at about the same time
(early 1963) as the other famous zero-address computer, the Burroughs
B5000 in America. Like many modern pocket calculators, a zero-address
machine allows the use of Reverse Polish arithmetic; this offers
certain advantages to compiler writers").
It used a 16 entry stack
and all operations were performed on the top element. To add locations
A and B and put the answer in C the commands were " A , B, +, =C ". A
quick way to decrement the top entry was " NEG, NOT " which changed the
sign and then reversed the bits. "NOT, NEG" incremented.
The unforgivable programming sin was not to control the stack properly resulting in "stack overflow" or "stack underflow".
||The KDF9 like the LEO III was a fully transistorised computer with core store and used M/T as the main storage media. Input was usually paper tape. Some systems used large fixed disks or drums for random access. 'Large' here is physical (1 ton) rather than storage capacity(24Mb).|
|Software||The KDF9 was
primarily a scientific rather than a commercial system - a
number of early FORTRAN and ALGOL compilers were written for it. The
Stafford machine was used for both types of computing. Universities
developed their own versions of the operating system.
Paper Tape Reader
24Mb Fixed Disk
KDF9 Computer Room
photos from Eric Foxley's site
||Below - Newcastle
of KDF9 (and Leo III)
The English Electric KDF9 Computer
Foxley - Misc Computing
Computer Conservation Society -includes list of Installations
Birmingham University - KDF9 with Disk