ICL 1900 Series George Implementation Manual GIM 8.1.2 to GIM 22.214.171.124
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ICL 1900 Series George Implementation Manual (GIM) - George 3
The ICL 1900 series had a lot in common with modern computers. One of the most notable differences from earlier machines was that included something recognisable as a modern operating system. The EXECutive was a privileged program which would run when the program started. It could then load jobs and run them.
The line allowed much more complicated operating systems to be run. The most advanced was GEORGE 3. This allowed programs to be run in both a batch and a multitasking mode called multiple online programming (MOP). This mode allowed multiple programs to be running at once, with access to physical devices controlled by pools - a program would request access to a teletype (for example) and one would be allocated to it from a pool, and then returned to the pool afterwards.
Several features were of note in the GEORGE series. The most interesting is the file store. This allowed for persistent storage in a location-independent manner. A job would request a file without needing to know whether it was stored on a tape or disk. Files stored on the disk would periodically be written to tales (one tape per file) by the dumper program. If they were not modified, they could then be deleted to free up space on the disk. If they were later accessed then the operator would be prompted to insert the tape. A similar feature was made available for commodity PCs in the early ’90s by Chili Pepper Software under the Infinite Disk brand, using floppy disks instead of tapes for the backup medium.
These were internal documents, many of which had not been published at the time and include the following series of documents:
GIM 8.1.2 to GIM 188.8.131.52
This exhibit has a reference ID of CH8959. Please quote this reference ID in any communication with the Centre for Computing History.