ELF operating system

ELF was a real-time multi-programming operating system for the PDP-11 (hence the name - 'elf' is German for 'eleven); generally, those with PDP-11 Memory Management (both kinds). It allowed processes to be created and terminated, and allowed them access to inter-process communication and timers; allocation and freeing of main memory was also provided. It was written in assembly language; applications could also be written in BCPL and BLISS-11.

It was originally intended to allow users at terminals to simultaneously utilize time-sharing systems on the ARPANET, using NCP (use of which was a standard capability under ELF). It was a successor to ANTS in this role. It also allowed users to save files on local mass storage; supported mass storage device controllers were TC11 DECtape, RF11 fixed-head disk, RK11 and RP11.

Work on it started in early 1973; it went into experimental service in early 1974, and by 1976 about 30 sites on the ARPANET were using it. It was later used by researchers at BBN to support the first routers on the experimental Internet.

ELF went through major changes during development. ELF-I had an emphasis on high throughput at the expense of modularity. ELF-II improved modularity but reduced throughput. VM ELF moved applications out of kernel space to separate user spaces.

Some ELF source code was found on backup tapes from the SAIL PDP-10. There is a possibly complete set of files from November 1974, and a smaller set of NCP code from August 1975.

See also

• ANTS terminal system
• Fuzzball
• MINITS
• MOS operating system

Further reading

• D. L. Retz, ELF System Development - this apparently online at Stanford, but access to it seems to currently be restricted

External links

• Structure of the ELF operating system
• ELF System Programmer's Guide
• An ARPANET Front-End for Large Computers, in Papers Presented at a Berkeley Workshop on Distributed Data Management and Computer Networks - pp. 57-70
• D. L. Retz, Operating system design considerations for the packet-switching environment
• ELF source code
  • ELF Kernel Programmer's Guide - January 1, 1976 version