 The ZX81 was designed to be small , simple , and above all cheap , using as few components as possible to keep the cost down . Video output was to a television set rather than a dedicated monitor . Programs and data were loaded and saved onto audio tape cassettes . It had only four silicon chips on board and a mere 1 KB of memory . The machine had no power switch or any moving parts ( with the exception of a VHF TV channel selector switch present on early " ZX81 USA " models and the Timex @-@ Sinclair 1000 ) and used a pressure @-@ sensitive membrane keyboard for manual input . The ZX81 's limitations prompted the emergence of a flourishing market in third @-@ party peripherals to improve its capabilities . Such limitations , however , achieved Sinclair 's objective of keeping the cost of the machine as low as possible . Its distinctive design brought its designer , Rick Dickinson , a Design Council award . 
