Glossary - G

Glossary of Multics acronyms and terms. Entries by Tom Van Vleck ([THVV]) unless noted.

gate

Segment that allows transfer of control between rings in a controlled fashion. Each gate segment has a vector of entries at its start. Now called "call gate" in the Intel world. Originated on Multics. Simulated on the 645 by the gatekeeper, supported in hardware on the 6180.

Gateway

Hardware project to build an ARPANet gateway, done at PMDC in 1979.

GCOS

Formerly GECOS, General Electric Comprehensive Operating System. After the 1970 merger, the "electric" was dropped. A batch processing system comparable to IBM IBSYS. More efficient that OS/360, but limited for many years to a single address space. Throughout Multics's life as a product it battled with GCOS for Honeywell resources and support of every kind.

GCOS 6

Operating system for the Honeywell Level 6 minicomputer. There were three versions of this OS; the "MOD600" version was influenced by Multics.

GCOS simulator

Also called the GCOS Environment Simulator, GES. Allows a user to run a GCOS program inside a single segment in Multics, intercepting the MME instructions that these programs issue and calling on Multics to e.g., open files or print output. Unbundled product. Similar in many ways to (the much later) Virtual 8086 mode on the Intel architectures. GCOS programs sometimes ran faster under the Multics GCOS simulator than they did on a real GCOS, because Multics paging I/O was more efficient than the GCOS mechanism.

GE

General Electric Co. Manufactured toasters, jet engines, nuclear power plants, and, for a while, computers. GE sold its computer division to Honeywell in 1970, in an event referred to as the "merger." Joke from that time: GE executives had a big meeting in Florida (Story: "Shangri-La and the Paris 645") to decide how to become number two in the computer business (this was in the days when it was "IBM and the seven dwarfs"). The solution they came up with: buy IBM and manage it for 6 months.

GEBUG

Debugging facility for 6.36 programs. Ran on CTSS. Don Wagner and Steve Kidd worked on this program.

GEMSOS

Gemini Computer's secure OS, influenced by Multics.

Genstat

[S. Brown] Genstat, "A General Statistical Program," was developed at the Rothamsted Experimental Station, Harpenden, Hertfordshire, UK. Rothamsted is an agricultural research centre. It was distributed by the Numerical Algorithms Group (NAG Ltd).

[THVV] Ported to Multics by Douglas Clark at Bath.

GESHUA

GE Six Hundred series Users' Association. Pre-merger name for HLSUA.

GIM

GIOC Interface Module. The code that operated the GIOC in the original 645 Multics.

Gimpelize

To arrange the items in a PL/I data structure so that no padding is generated, by grouping them with all the items of highest boundary alignment first, then next highest, and so on. Named after Jim Gimpel of BTL, who stated the rule in 1966.

GIMPSPIF

[RHG] GIOC to IMP Special Interface. The hardware interface to the ARPANet IMP for 645 Multics. Operational in October of 1971. (Designed, if I recall correctly, by MIT student Abhay Bhushan.) Replaced by the ABSI on the 6180.

GIOC

Generalized I/O Controller. This box did all the I/O for the 645. Some programmers pronounced this by spelling it out, but the field engineers tended to say "gee-yock."

Glim

Statistical stuff done by Douglas Clark at Bath?

GM

General Motors Corporate/EDS. Big Multics customer. Detroit, MI. See GM site history.

GMCRB

Greater Multics Change Review Board. Open to all developers. (MAB-048-02)

graphics

Multics graphics were heavily influenced by the Electronic Systems Laboratory design for the Kludge on CTSS. The Multics graphics system created a device independent representation and then translated it to device codes at display time. It was intended that this should work as well on an ARDS as on a vector scope.

[Joe Dehn] Graphics drivers (called "graphic interface modules") were written not only for displays like ARDS, but also for hardcopy devices like Calcomp plotters, and even for plain character tty-like terminals (pretty poor resolution, I'll admit, but I did write one).

[THVV] I wrote a Multics graphics driver that translated into opcodes for a microfilm plotter at the MIT Comp Center. You could do some iocall attach commands and run your program, and it would output the codes into a file you could put on tape and send to the plotter. I may still have a sheet of paper with the output of the globe program.

GRTS

GCOS remote job entry supervisor used in the 1970s. A very idiosyncratic RJE interface to GCOS. You could log in to Multics over this facility, but it was very hard to use.

GTSS

GCOS Time Sharing System. A TSO-like time-sharing environment within GCOS. Simulated on Multics in the GCOS simulator, started by the Multics gtss command. Unbundled product.

Guardian

CISL/MITRE/USAF project that added AIM, the Access Isolation Mechanism, to Multics, and began design of a high assurance minimized security kernel. Article: "Multics Security Evaluation".