OS4000 facts for kids

OS4000 is a special computer program, like the brain of a computer, made by GEC Computers Limited. It was first released in 1977. OS4000 was designed for their GEC 4000 series minicomputers. These were powerful computers for their time. OS4000 helped these computers do many tasks at once. It was used for a long time, until the late 1990s. Today, it is mostly supported but not actively developed.

The Story of OS4000

Before OS4000, GEC 4000 computers used simpler systems called COS and DOS. These were mainly for one person to use at a time. They helped control machines in factories.

OS4000 came out in 1977. It used many parts from the older DOS system. But it added new features. Now, many people could use the computer at the same time. It also had a new way to give commands to the computer. This was called OS4000 JCL. It also had a better way to organize files, like folders on your computer.

OS4000 Releases Over Time

• OS4000 Release 3 came out around 1980. It allowed different OS4000 systems to connect and work together. This was useful for big computer centers. For example, at University College London, many computers were linked. They served over 100 users at once. This linking also helped make systems more reliable.
• OS4000 Release 4 arrived around 1983. It let even more users (up to 150) connect to the system. It also improved how the computer handled big jobs. This release also supported a newer, more powerful computer, the GEC 4090. This computer could handle more data at once.
• OS4000 Release 5 changed how files were stored. It made it easier to use larger storage disks.
• OS4000 Release 6 added support for computers with two main processors. This made the systems even faster.

OS4000 was created in the UK. The development teams worked in Borehamwood and Dunstable.

How OS4000 Works

OS4000 was built to work closely with the special features of the GEC 4000 series computers. These computers had a unique part called "Nucleus." Nucleus was like a built-in brain that handled many basic computer tasks. This meant OS4000 didn't need to do those jobs itself.

Nucleus could manage up to 256 different tasks or "processes" at once. It would schedule them automatically. OS4000 worked entirely within these processes. Special "system tables" told Nucleus how to set things up. These tables also controlled which processes could talk to each other.

For example, a program that controls a disk drive was a process. The system tables would allow it to talk to the disk drive. If a process stopped working, Nucleus would tell the main system. The system could then decide what to do, like restart the process. Other parts of the system, like file management and connecting to terminals, also ran as separate processes.

OS4000 also managed how the computer used its memory. It could use both fast, direct memory and slower memory stored on disks. This allowed programs to use more memory than was physically available.

OS4000 could handle many types of tasks at the same time. It could run very urgent "real-time" tasks. These are tasks that need to happen instantly, like controlling factory machines. It could also handle tasks shared by many users. This made OS4000 great for developing and running real-time programs.

Organizing Files

OS4000 uses its own special way to organize files. Files are stored in different-sized blocks. This means some files might use small blocks, and others use larger ones.

When you create a file, you tell the system how much space it needs. Files can be stored in many small pieces or in one continuous block.

The file system is organized like a tree, with folders inside folders. Each part of a file's name is limited to 8 characters. A dot (`.`) separates the parts of the name. Every file path starts with a "context pointer." This points to a place in the file system. Then come "catalogues" (like folders), and finally the filename.

Each disk on the system has its own file system. One disk must be named `SYSTEM`. This disk holds important files that OS4000 needs to run. Users usually have their own areas where they can store files. This keeps their files separate from other users' files and system files.

Files in OS4000 have different "types." This helps the system understand what kind of information is in the file. For example, there are "logical" files that hold records. These can be "sequential" (read in order) or "random" (you can jump to any record). Files are also marked as "text" or "binary." This stops programs from trying to read a binary file as if it were text.

There are also special links, like shortcuts on your computer. These can point to other files or folders.

OS4000 also has a temporary file system. These files are stored in a special area and are deleted when a user logs out. Each user has their own private temporary space.

Using OS4000

Here is an example of what it looked like when someone logged into an OS4000 system:

SESSION STARTING

OS4000 Rel 6.5 A036 on A7 SUN 17 MAY 2009 11:06:27
Logging in
user SMAN
password

ID last used SAT 16 MAY 2009 22:21:43
STARTED - SUN 17 MAY 2009 11:06:31
OS4000 Rel 6.5 A036 on A7 SUN 17 MAY 2009 11:06:31
Only an authorised person should be logged in as SMAN
READY
EXAMINE
EXAMINE version 305

Catalogue  USER
--------------------------------------------------------------------------------

DATA      Odp   GEST      Odp   IPL       CAT   MAILAREA  CAT   MCODE     CAT
OPER      CAT   PDA1      Odp   POSTCAT   Odp   POSTFOLD  CAT   SEBACKUP  LST
SMAN      CAT   SOURCE    Odp   SOURCE1   Odp   SPOOL     Odp   SUNDRY    Odp
SYS       CAT   SYSFILES  CAT   SYSGEN    Odp   SYSGEN1   Odp   TEST      Odp
USEA      Odp   USEB      Odp   USEC      Odp   WORK      Odp   X25       CAT
YBTS      CAT

--------------------------------------------------------------------------------
READY
***TO REMAIN ONLINE TYPE COMMAND WITHIN 5 MINS
***STOPPED
CPU used: 3 ieu  elapsed time used: 15 mins
User SMAN terminal   2 logged out  SUN 17 MAY 2009 11:21:31

In this example, a user named `SMAN` logged in. They typed the `EXAMINE` command to see a list of files and folders. Then, the session ended because the user didn't type anything for 5 minutes.

When a user logged in, a program called `SYS.COMM` would start. This program read commands typed by the user. Some commands were built into `SYS.COMM`. If a command wasn't built in, the system would find and run another program.

Where OS4000 Was Used

OS4000 was used in many important areas:

• Controlling Machines: More than half of all OS4000 systems were used for Process control. This means they controlled machines in factories, especially in steel production.
• Data Networks: OS4000 was used in systems that managed data communication networks.
• Emergency Services: It powered Civil Command and Control systems. For example, it helped fire services connect emergency calls to fire stations.
• Information Services: OS4000 was used for early online information systems like Prestel in the UK. These systems allowed people to access information using their TVs.
• Education and Research: Many schools and research places used OS4000 on their minicomputers.

Other Versions

OS4000 was also adapted to run on a different computer called the GEC Series 63 minicomputer. This version was called OS6000. It needed extra software to work because the GEC Series 63 didn't have the special "Nucleus" feature. GEC Computers stopped developing OS6000. The source code (the original programming instructions) was given to Daresbury Laboratory. They continued to update it for their own use.

See also

• GEC 4000 series minicomputers
• Babbage (programming language)
• GEC Computers Limited