The ZX81 was a home computer made by Cambridge-based company Sinclair Research and released in 1981. It was notable for its low price and small size, and in the UK was the first computer to be sold in high street stores such as WH Smith.
The ZX81 was the brainchild of Clive Sinclair, who had previously created the ZX80, a very similar machine which was launched in 1980. The ZX81 used a Zilog Z80A microprocessor and came with 1KB of onboard RAM, expandable to 16KB. It could be connected to a TV or monitor, and came with a simple membrane keyboard which could be used to input programs and data.
Despite its limitations, the ZX81 was a popular machine, selling over 1.5 million units worldwide. It was succeeded by the ZX Spectrum, in 1982.