 High @-@ profile advertising was central to the marketing campaign . Although Sinclair Research was a relatively small company , it had a long @-@ standing policy of using large @-@ scale advertisements that stood out in stark contrast to the more muted advertisements of other manufacturers . Superlatives , exhortations , appeals to patriotism , testimonials , eye @-@ catching drawings and photographs on double @-@ page spreads , varying from month to month , were used to drum up mail order business for Sinclair . The launch advertising for the ZX81 illustrates this approach . A photograph of the ZX81 alongside the official Sinclair peripherals dominated the centre of a double @-@ page spread . The value for money of Sinclair 's products was emphasised by the prices being printed in larger type than any other text on the spread . The ZX81 's benefits were promoted with the aspirational slogan " Sinclair ZX81 Personal Computer – the heart of a system that grows with you " . The advertisement highlighted ZX81 BASIC Programming , the manual written by Steve Vickers , as " a complete course in BASIC programming , from first principles to complex programs . " The educational benefits of the ZX81 were stressed ( " it 's still very simple to teach yourself computing " ) and its technical advantages were explained in relatively non @-@ technical terms . For instance , the ZX81 's idiosyncratic method of typing commands with a single keystroke – the result of the memory @-@ saving method of using one @-@ byte tokens to represent keywords – was presented as " eliminat [ ing ] a great deal of tiresome typing " . The ZX81 's British character was emphasised ; it was " designed by Sinclair and custom @-@ built in Britain . " Sinclair 's advertising in the United States provides an illustration of how the company perceived the ZX81 's purpose : 
