Sinclair ZX81: semigraphical / pseudographical characters
"If you press GRAPHICS (shifted 9) then the cursor will come up as 
: this means graphics mode. If you type in a symbol it will appear in its inverse video form, & this will go on until you press GRAPHICS again or NEWLINE. RUBOUT will have its usual meaning. Be careful not to lose the cursor amongst all the inverse video characters you've just typed in. ...
Right at the beginning are space & ten patterns of black, white & grey blobs; further on there are eleven more. These are called the graphics symbols & are used for drawing pictures. You can enter these from the keyboard, using graphics mode (except for space, which is an ordinary symbol using the 
cursor; the black square is inverse space). You use the 20 keys that have graphics symbols written on them. For instance, suppose you want the symbol 
, which is on the T key. Press GRAPHICS to get the 
cursor, & then press shifted T. From the previous description of the graphics mode, you would expect to get an inverse video symbol; but shifted T is normally <>, a token, & tokens have no inverses: so you get the graphics symbol instead."
(Steven Vickers, 1981, Sinclair Research Limited)
Fig.1 "graphics mode" table from Steven Vickers (1981). "Sinclair ZX81 BASIC Programming", Second Edition 1981, Copyright 1980 Sinclair Research Limited (converted to HTML by Robin Stuart).
2). Matthew Eagles (2008). "ZX81 VDU" TrueType font which replicates the letters, numbers etc. displayed on the screen of the ZX81.
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Simon PerkinsSHARE
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(Computer History Museum)
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