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Sinclair ZX81 User Manual

Sinclair ZX81
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The cursor can also be used for correcting mistakes: type ++2, to get
PRINT
++2
on the bottom line, Pretty incomprehensible stuff, and when you press
NEWLINE
you get
The is the syntax error marker (the syntax is the grammar of the message, saying which are allowed
and which are not), and shows that the computer got as far as '
PRINT
', but after that decided that it was
not a proper message.
What you want to do of course is rub out the first +, and replace it by - let us say - 3. First you have to
move the cursor so that it is just to the right of the first +; there are two keys, and (shifted 5 and shifted
8), that move the cursor left and right. Holding
SHIFT
down, press the key twice. This moves the cursor
left two places to give you
PRINT
++2
Now press the
RUBOUT
key (shifted 0), and you will get
PRINT
+2
RUBOUT
rubs out the character (or keyword) immediately to the left of the cursor.
If you now press 3 this will insert a '3', again immediately to the left of the cursor, giving
PRINT
3+2
and pressing
NEWLINE
gives the answer (5).
The key (shifted 8) works just like the key, except that it moves the cursor right instead of left.

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Sinclair ZX81 Specifications

General IconGeneral
ProcessorZilog Z80A
Processor Speed3.25 MHz
ROM8 KB
InputMembrane keyboard
StorageCassette tape
Power Supply9V DC
Dimensions167 mm x 40 mm x 175 mm
Release Year1981
ManufacturerSinclair Research
Weight350 g
Operating SystemSinclair BASIC
RAM1 KB
PortsTV out, expansion port
DisplayTelevision (RF modulator output)

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