 The ZX81 is a home computer produced by Sinclair Research and manufactured in Scotland by Timex Corporation . It was launched in the United Kingdom in March 1981 as the successor to Sinclair 's ZX80 and was designed to be a low @-@ cost introduction to home computing for the general public . It was hugely successful , and more than 1 @.@ 5 million units were sold before it was discontinued . The ZX81 found commercial success in many other countries , notably the United States , where it was initially sold as the ZX @-@ 81 . Timex manufactured and distributed it under licence and enjoyed a substantial but brief boom in sales . Timex later produced its own versions of the ZX81 for the US market – the Timex Sinclair 1000 and Timex Sinclair 1500 . Unauthorised clones of the ZX81 were produced in several countries . 
