English Electric KDF8 facts for kids

The KDF8 was an early computer made in Britain by a company called English Electric. It was based on an American computer, the RCA 501. The idea was to save time and money by using an existing design. However, it took a long time to build these computers. Because of this, other companies soon made faster and better computers.

Only a few KDF8 systems were sold during its five years of production. Later, English Electric's computer part joined with other companies. This group eventually became ICL.

The Story Behind the KDF8 Computer

In the late 1950s, English Electric started two big computer projects.

One project was to build a version of the RCA 501 computer. They called it the KDP10. The "KDP" stood for Kidsgrove Data Processing. This computer was made for business tasks, like handling numbers and text. English Electric changed the RCA design to use parts made in the UK.

The first KDP10 was ready in 1961. In 1964, its name changed to KDF8. They kept selling it until 1965. The KDF8 was almost the same as the RCA 501. English Electric built it under a special agreement. This allowed them to offer a full range of computers to their customers. They didn't have to spend money designing a brand new machine.

The KDF8 cost about £400,000 back then. That was a huge amount of money! Only 13 of these computers were ever sold.

Another large computer from Kidsgrove was the KDF9. This one was mainly for science work.

One KDF8 computer was set up at English Electric's computer center in Kidsgrove, Staffordshire. Over the years, this center changed names many times due to company mergers. It became English Electric Leo Marconi (EELM), then International Computing Services Limited (ICSL), and finally Baric.

How the KDF8 Worked

The KDF8 was a transistor-based computer. This means it used small electronic switches called transistors. Older computers used bigger, hotter vacuum tubes. It also used magnetic core memory for its main storage.

Processor and Memory

The KDF8 computer at Kidsgrove had its memory upgraded. It went from 64,000 to 96,000 units of memory. This was the most memory it could hold at the time. The KDF8 used a special number system called octal (base eight).

Each command for the computer was a fixed length. It was ten octal characters long. These commands were made for business use. They could do math like adding and subtracting with numbers of different lengths. They could also handle text information efficiently.

The KDF8 was a batch processing computer. This means it could only run one program at a time. It could do one math task, and also read or write data at the same time. This usually involved magnetic tapes. Programmers had to be very skilled to make all these tasks happen together.

Over time, the KDP10 at the service center was updated. Its main parts were changed from germanium transistors to silicon transistors. This made it faster. The machine cycle, which is how fast it processes information, was also sped up.

Programmers had to be very careful. They had to write code to handle reading, writing, and computing all at once. If they made a mistake, the computer might just stop working.

Connecting to the KDF8: Peripherals

The KDF8 didn't use modern hard drives. It stored information on magnetic tapes. These tapes came on large reels. Each reel was about one inch thick and nine inches across. They could hold up to 2,400 feet of tape! Both programs and data were stored on these tapes.

The KDF8 at Kidsgrove had eight magnetic tape units connected to it. Each unit could read or write 40,000 characters per second. Each tape unit was about 6 feet tall and 2 feet wide. The main computer parts were also large. This meant the KDF8 needed a very big, air-conditioned room.

Other devices could also be connected to the KDF8:

• A paper-tape reader could read data and programs. It was very fast, reading 1,000 characters per second.
• An operator's teleprinter was like a typewriter. It let the computer show messages to the person running it. The operator could also type in short commands.
• An on-line printer was mainly used to print out information when a program failed. This helped programmers find errors.

Both the on-line and off-line printers were impact printers. They printed one line at a time, either 120 or 160 characters wide. They only used capital letters. The paper came in long, continuous sheets. It had holes on the sides for the printer to pull it through.

Running Programs on the KDF8

The KDF8 didn't have an operating system like computers today. An operating system helps manage programs and hardware. Instead, a person called an operator had to start programs manually.

Operators also had to clear the computer's memory between programs. They had to load and change the magnetic tapes. They also controlled the off-line printers.

Some standard programs were available. These were mostly made in the USA by the RCA company.

• A sort-merge program could organize very large amounts of data. It could sort information in different ways.
• An assembler-language compiler called EZ-Code helped programmers write code. At first, it wasn't used much because it took a long time to prepare programs. But later, it became more popular. Programmers often had to make small changes to programs using paper tape.
• A COBOL compiler was also available. COBOL is a programming language for business. This was rarely used. One special program written in COBOL helped design parts for later English Electric computers.

To make the computers work as fast as possible, programmers created special programs. These handled tasks like payroll, sales records, and managing stock. Some programs could even handle data for many different customers at once.

Operating the KDF8 Computer

To start a program, the operator would load a special tape. This tape had a small program called a "bootstrap loader." This program helped the computer get ready.

Operators had to follow written instructions very carefully. These instructions told them which program tape and data tapes to load. They also said which devices to use. The operator would then load the tapes and start each program by hand from the control panel.

The control panel was a large display with many buttons and lights. It showed the computer's status in a special code (binary grouped as octal). When a program was running, these lights would flash quickly in different colors.

The operator could use buttons to type information directly into the computer's memory. To enter just one command, the operator had to carefully key in each part of the command. This was a very detailed and precise job!

See also

• Early British computers