Home Hardware Peripherals Software Publications Projects

On This Day - 21st June

« Previous Day Next Day »
1948

First electronic RAM successfully used

The Manchester Small-Scale Experimental Machine (SSEM), better known as the Manchester Baby, successfully ran its first program using the Williams–Kilburn tube, an electronic read/write memory based on a cathode-ray tube. At 11:00, Tom Kilburn's 17-instruction program was executed from memory, demonstrating the practical use of electronic random-access memory and the stored-program principle.

The Baby's memory could store 1,024 bits, with the program and working data held electronically rather than on punched tape or through hard-wired connections. The successful demonstration at the University of Manchester became a fundamental milestone in the development of modern computer memory.
Source: University of Manchester; IEEE History Center — 21 June 1948
The University of Manchester records that the Manchester Baby began running its first program at 11:00 on 21 June 1948. IEEE's historical account identifies the event as the first computer execution from addressable read/write electronic memory and notes that the demonstration validated the Williams-Kilburn tube random-access memory. The first program, written by Tom Kilburn, calculated the highest proper factor of 2¹⁸ and took approximately 52 minutes to produce its result.
RAM Random Access Memory Williams-Kilburn Tube Manchester Baby SSEM Computer Memory Stored Program University of Manchester
1984

Amstrad CPC 464 goes on sale in the UK

The Amstrad CPC 464 went on sale in the United Kingdom, becoming Amstrad's first home computer. The 64K machine incorporated a cassette recorder into its keyboard and was sold as a complete system with either a green-screen or colour monitor. The first public sales took place at Rumbelows on Edgware Road, London, where the initial supply sold out within three hours. The CPC 464's distinctive combination of a full-size keyboard, integrated cassette recorder and compact all-in-one design would later be echoed in Amstrad's ZX Spectrum +2, introduced after Amstrad acquired Sinclair's computer business in 1986. The similarities in the +2's design reflect Amstrad's established approach to home-computer design and the company's desire to give the Spectrum a more integrated form, while retaining its own distinct identity.
Source: Amstrad
Amstrad's own historical account states that the CPC 464 was launched publicly at Westminster School on 11 April 1984, but that it first went on sale in the UK on 21 June 1984. Rumbelows was given the initial retail launch at its Edgware Road branch, with the first machines selling out within approximately three hours.
Amstrad CPC 464 Rumbelows Home Computer 64K

Also in this month

Other historical information recorded for June.

1977

Science of Cambridge incorporated

In June 1977, Science of Cambridge was incorporated by Clive Sinclair and Chris Curry. The company was established following the financial difficulties that had affected Sinclair Radionics and became the beginning of a new phase in Sinclair's electronics business. Despite its name, the company was not primarily a scientific research organisation; it developed and marketed innovative consumer electronics products.

Science of Cambridge is particularly important in the history of British home computing because it produced the MK14, a low-cost single-board computer based around the National Semiconductor SC/MP processor. Introduced in 1978, the MK14 was sold as a kit and helped demonstrate the growing demand for inexpensive personal computers. Chris Curry subsequently became increasingly involved in the computer side of the business, eventually leaving to establish Acorn Computers with Hermann Hauser.

Science of Cambridge later changed its name to Sinclair Computers and subsequently became Sinclair Research. The company's development therefore provides a direct link between Clive Sinclair's earlier electronics business and the computers that followed, including the ZX80, ZX81 and ultimately the ZX Spectrum.
Source: Companies House / Sinclair historical records
Science of Cambridge was incorporated in 1977 and became the company responsible for the MK14 before evolving into Sinclair Computers and later Sinclair Research.
Science of Cambridge Clive Sinclair Chris Curry Sinclair MK14 SC/MP Sinclair Computers Sinclair Research ZX80 ZX81 ZX Spectrum British computing
1978

Science of Cambridge launches the MK14

**Science of Cambridge launches the MK14**

Science of Cambridge's MK14 was the company's first microcomputer and an important early step towards the Sinclair ZX80, ZX81 and ZX Spectrum. The project originated with Ian Williamson, who had developed a small computer based around National Semiconductor's SC/MP microprocessor and components from a Sinclair calculator. Chris Curry recognised its potential and persuaded Science of Cambridge to develop it as a commercial kit. The resulting MK14, or Microcomputer Kit 14, was aimed primarily at electronics enthusiasts and computer hobbyists.

Launched in 1978 for around £40, the MK14 provided a surprisingly capable introduction to microcomputing at a very low price. The basic kit included a National Semiconductor SC/MP processor, 256 bytes of RAM, a 512-byte monitor program and an eight-digit, seven-segment LED display operated through a 20-key hexadecimal keyboard. Optional expansion boards provided additional RAM, I/O and interfaces, including the possibility of connecting the computer to a television display and cassette recorder. The MK14 went on to sell tens of thousands of units and helped establish the market that Science of Cambridge would soon exploit with the ZX80.
Source: Electronics Today International — 30 September 1978
Contemporary review states that the MK14 had been launched earlier in 1978. Exact launch day not established.
MK14 Microcomputer Kit 14 Science of Cambridge Sinclair Clive Sinclair Chris Curry Ian Williamson SC/MP INS8060
Page Revised: 07/09/2026

Mister Spectrum © 2022–2026 Kevin R. Carr