OS4000 facts for kids

OS4000 is a special kind of operating system. It was created by GEC Computers Limited in 1977. This system was made for their GEC 4000 series of minicomputers.

OS4000 was designed to replace an older system called GEC DOS. It was updated until the late 1990s. Since then, it has mostly been used for support, not for new development.

A Look Back: The History of OS4000

Before OS4000, the GEC 4000 computers used systems called COS and DOS. These were simple operating systems. They let one user do many tasks at the same time. They were mainly used for controlling industrial processes.

OS4000 first came out around 1977. It used many parts from the older DOS system. But it added new features. These included letting many users access the computer at once. It also had a new way to run commands and manage files.

OS4000 Releases and New Features

OS4000 Release 3 came out around 1980. It added something called Linked-OS. This allowed several OS4000 systems to work together. For example, University College London used it. They connected a main file server to many user systems. This let over 100 people use the system at the same time. Linked-OS also helped make systems more reliable for process control.

OS4000 Release 4 arrived around 1983. It increased the number of users that could connect. It also improved the system for running many tasks in a batch. This release also supported a new processor, the GEC 4090. This processor could handle 32-bit information.

OS4000 Release 5 introduced a new file system called CFSX. This made it easier to use larger disk drives.

OS4000 Release 6 added support for computers with two processors. This meant the GEC 4190D systems could run even faster.

OS4000 was developed in the UK. The main offices were in Borehamwood and Dunstable.

How OS4000 Works: Architecture

OS4000 was built to work closely with the GEC 4000 series computers. These computers had a special feature called Nucleus. Nucleus was a combination of hardware and software built into the computer itself. It handled many basic tasks that operating systems usually do.

Because of Nucleus, OS4000 didn't need to do everything. Nucleus could manage up to 256 different tasks, called processes. It also decided which process got to run when. OS4000 worked by running its own parts as these processes.

Nucleus also controlled how different processes could talk to each other. It managed how programs accessed parts of the computer, like disk drives. If a program stopped working, Nucleus would tell the main system. The system could then decide what to do next.

OS4000 also managed how programs used the computer's memory. It could use both main memory and disk space for programs. This allowed the system to run many different types of programs. It could handle real-time tasks that need to happen instantly. It could also manage tasks shared by many users. This made OS4000 good for developing and running complex applications.

Organizing Files: The Filesystem

OS4000 uses its own special way to store files. It organizes files into different parts on the disk. Files can also have different block sizes. This means they can use space on the disk in different ways.

When you create a file, you decide how much space it gets. Files can be spread out or stored in one continuous block.

The filesystem is organized like a tree, with folders inside folders. These folders are called catalogues. File names and folder names are usually limited to 8 characters. They use a period (`.`) to separate parts of the path, just like `folder.subfolder.file`.

Each disk on the system has its own separate filesystem. One disk must be named `SYSTEM`. This disk holds important files that OS4000 needs to run. Other disks can store user files or data. Users are given specific starting points, called initial context pointers. They can only see files and folders below these points. This helps keep users' files private.

Files in OS4000 have different types. This tells the system what kind of information is inside. 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 can also be text or binary. This helps programs know how to use the file. For example, LST means Logical Sequential Text.

There are also special links, like shortcuts. References (REF) point to other files or folders. Off Disk Pointers (ODP) are similar but are for special system files. Later versions also added links like those found in Unix systems, called symlinks.

OS4000 also has a temporary filesystem. This is for files that are only needed for a short time. These files are deleted when a user logs out or the system restarts. Temporary files usually start with a percent (`%`) or ampersand (`&`) sign.

Using OS4000: Multi-access Environment

Here is an example of what it looked like when a user logged into OS4000:

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` logs in. They then type the command `EXAMINE`. This command shows a list of files and folders in their current directory. After a while, the system logs the user out because there was no activity.

When a user logs in, a program called `SYS.COMM` starts. This program lets the user type commands. Some commands are built into `SYS.COMM`. For other commands, the system loads and runs separate programs.

What OS4000 Was Used For

OS4000 was used in many important areas:

• Controlling Processes: More than half of all OS4000 systems were used for real-time Process Control. This meant controlling things like steel production in factories.
• Packet Switches: OS4000 was used in systems that managed data networks, like X.25 packet switches. These systems helped send data efficiently.
• Command and Control Systems: It powered systems like those used by fire services. These systems helped connect emergency calls to fire stations.
• Public Information Systems: OS4000 was used for systems like Prestel in the UK. These were early online information services, similar to today's internet.
• Multi-User Computers: Many schools and research places used OS4000. It allowed many students and researchers to use the same computer at once.

OS4000 on Other Computers

OS4000 was also adapted to run on another computer, the GEC Series 63 minicomputer. On this system, it was called OS6000. The GEC Series 63 didn't have the special Nucleus hardware. So, a software version of Nucleus had to be added.

GEC Computers eventually stopped developing OS6000. The source code (the original computer instructions) was given to Daresbury Laboratory. They were a major user of OS6000. They continued to update it to match the OS4000 releases.

See also

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