Edinburgh Multiple Access System facts for kids
The Edinburgh Multi-Access System (EMAS) was a special computer program, called an operating system, that ran on a very large computer known as a mainframe computer. It was created at the University of Edinburgh in Scotland. EMAS started working in 1971.
EMAS was a powerful system that allowed many people to use the computer at the same time. It helped the University of Edinburgh and the University of Kent with their computing needs. The University of Kent was the only other place that used EMAS.
How EMAS Started and Grew
EMAS first ran on a large computer called the ICL System 4/75. This computer was designed similarly to the IBM 360. Later, EMAS was updated and ran on newer ICL 2900 series of mainframes. This new version was called EMAS 2900 or EMAS-2. It was used until the mid-1980s.
Near the end of its time, an even newer version, EMAS-3, was made. It was adapted to run on other large computers like the Amdahl 470 and later the IBM System/370-XA. The University of Kent helped with this, but they never actually used EMAS-3. It also ran on the National Advanced System (NAS) VL80. The very last EMAS system, at Edinburgh, was turned off in July 1992.
The system at the University of Kent began working in December 1979. It ran on an ICL 2960, which was one of the smaller ICL 2900 computers. This computer had 2 megabytes (MB) of memory. It could perform about 290,000 instructions every second. Even with this, it reliably supported about 30 users at once. In 1983, the system got an upgrade. It received an extra 2 MB of memory and a second main processing unit, called an OCP or CPU. This allowed it to do more tasks at the same time. The University of Kent's EMAS system was stopped in August 1986.
Cool Features of EMAS
EMAS was mostly written in a special computer language called Edinburgh IMP. Only a few very important parts used a more basic computer code. EMAS had many features that were very advanced for its time.
Some of these features included:
- Dynamic linking: This allowed programs to connect to other parts of the system while they were running.
- Multi-level storage: It managed how data was stored in different places, like fast memory and slower storage.
- Efficient scheduler: This part of the system decided which tasks the computer should work on next.
- Separate user-space kernel: A core part of the operating system, called the 'director', worked separately for each user.
- User-level shell: Users could type commands into a program called the 'basic command interpreter' to tell the computer what to do.
- Comprehensive archiving system: It had a good way to save and store old files.
- Memory-mapped file architecture: This made it easier for programs to work with files as if they were directly in the computer's memory.
Because of these advanced features, people who supported EMAS believed it was better than Unix for its first 20 years. Unix is another well-known operating system.
What EMAS Left Behind
The Edinburgh Computer History Project is now trying to learn from the EMAS project. They have made the complete computer code for EMAS available online for anyone to look at. This helps people understand how this important system worked.
See also
