ICT 1900
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ICT 1900 is the name given to a series of mainframe computers released by International Computers and Tabulators (ICT) in the 1960s. These varied in computing power and the models included:
- ICT 1901
- ICT 1902
- ICT 1903
- ICT 1904
- ICT 1905
- ICT 1906
- ICT 1907
- ICT 1909 (this machine had a hardware floating point arithmetic engine so it was suitable for scientific use.)
The first machine was in fact the 1904 which was a Canadian design from the Ferranti-Packard company, originally called the FP6000. The story is that this machine with 'core store memory' fired up with its program still in store after its sea freight journey from Canada.
One feature of these mainframes was the common instruction set throughout the range meaning that programs written and compiled on one machine would run unchanged on any other. In fact the hardware was different between machines. To achieve this a program termed "the executive" or exec encapsulated the hardware and supplied software routines to supplement the hardware supplied instructions.
By 1968 ICT had merged with English Electric computers and become ICL.
Enhanced versions of the 1900 series subsequently appeared with an A suffix, an E suffix, an F suffix (for floating point), a T suffix, and an S suffix, e.g.
Stevenage designed and built machines
- ICL 1901A
- ICL 1901S/T?
- ICL 1902A
- ICL 1902S
- ICL 1902T
- ICL 1903A
- ICL 1903S
West Gorton (Manchester) built machines
- ICL 1903T
- ICL 1904A
- ICL 1904T
- ICL 1904S
- ICL 1906S
The 1900 Series were 24-bit word machines (supporting 4 6-bit characters per word) and using octal for binary short-hand, as opposed to the IBM Systems using 8-bit bytes and hex. Basic memory on the smaller machines was 16K words (or 64 kilobytes equivalent), and there were even 8K word versions sold (although most actually had 16K memory factory installed in readiness for the certain upgrade order that followed!) - early machines using 'core-store' memory (ferrite rings on a copper wire matrix) and operated on binary hand-switches on the mainframe cabinet. Despite the apparent small memory size, quite sophisticated applications were run on the equipment and computer programmers paid great attention to the efficient use (and reuse) of memory.
I/O consisted of 80 column cards as 40 column cards (with round holes) were unable to cope with the full 64 character set, a card punch and 8 track paper tape - print was from a solid barrel line printer (120 columns wide).
The first commercial sale was made in 1964 to the Morgan Crucible Company and consisted of a 16k word 1902 with an 80 column 980 card/minute reader, a card punch, a 600 line/min printer and 4 x 20Kbs tape drives. It was soon upgraded to a 32K word memory and a floating point unit to allow for some scientific work. Incidently this company was also the first business to order ICT's previous computer, the HEC4 (later ICT 1201) in 1955.
Disk capacity was also very limited (early units supporting 4 or 8Mb removable multi disc packs) (1903 system first) (and Steve Hillel crashed the first unit when demonstrating it to his manager) and similar attention to ensuring the efficient use of disk space was common. Early machines used storage on reels of magnetic tape and were then augmented by direct access devices (disks) typically with disk capacities of 1.6Mb, 4Mb and 8Mb were the order of the day. By the time 30Mb packs were available they occupied a cabinet 4 feet high (MEDS - Multiple Exchangeable Disk Store).
After ICL had introduced the 2900 series of computers during the 70's the 1900 series in fact lived on as there was such a wealth of software written for it. ICL introduced the 2903 and 2904 which were designed and built in Stevenage, which were really successors to the 1902A/3A machines as they had the same target instruction set, while the 2960 machine from West Gorton, which had a new native instruction set, could also run 1900 series code as an emulation. Stevenage later designed and built the 2940/50 based on the same central processor as the 2960, but again able to emulate its predecessor 1900 series code.
Programming languages included the assembly type language PLAN (Programming LAnguage Nineteen-hundred) and latterly COBOL for the development of commercial-orientated systems while ALGOL and FORTRAN were used for scientific work.
The basic operating System was called "Executive" and supported "multiprogramming", i.e. it was capable of running as many as 4 programs concurrently, on the 1904 and larger machines. Later on (starting about 1968) advanced features (e.g. batch processing, spooling) were provided by a privileged ("trusted") program called GEORGE (GEneral ORGanisational Environment), and so GEORGE1, GEORGE2/GEORGE2S, GEORGE3 and GEORGE4 - paging etc. were born.
The University of Leeds has created a software emulator that runs George 3 on a PC, which can be found at http://www.icl1900.co.uk/g3/preserve.html .
Contents |
[edit] Operating systems and software
[edit] The Georges
- George I (GEneral ORGanisational Environment)
- George IS
- George II
- George 2S
- George 2+ (from Dataskil)
- George 3
- George 4
[edit] Utilities and compilers
- XEKB COBOL compiler
- XEMC Extended mode COBOL compiler
- XPCK Consolidator
- XPLG PLAN compiler (Programming Language Nineteen Hundred) Assembly language
- XPLT PLAN 4 complier
- YMTC tape copier
- YMTV tape formatter
- XPJC Disc file allocator
- XPJW Backup and restore utility
[edit] Application software
- SCAN Stock control system
- PERT Project management system
- PROSPER Financial planning system (forerunner of today's spreadsheet programs)
- NIMMS Production control system (Acronym: 1900 Integrated Modular Management System)
- More detailed history is available at [1] (requires Internet Explorer)
