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Sinclair ZX81 User Manual

Sinclair ZX81
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which is evaluated as
Summary
Strings
Operation: + (for strings)
Functions:
LEN
,
VAL
,
STR$
Exercises
1. Type
LET
A$="2+2"
& then
PRINT
A$;" = ",
VAL
A$
Try changing A$ to more complicated things & doing the same, e.g.
LET
A$="
ATN
1*4"
(The answer here should be .)
2. The string "" with no characters is called the empty or null string. It is only string whose length is 0.
Remember that spaces are significant and an empty string is not the same as one containing spaces.
Do not confuse it with the quote image,
""
(a single token, shifted Q). This is a special device to get over
the fact that you cannot write an ordinary string quote in the middle of a string (why not?). When the quote
image appears in a string that has its quotes at the end (for instance in the listing of a program), it shows
up as two quote symbols, to distinguish it from the ordinary quote; but when it is displayed by a
PRINT
statement, it is as just one quote symbol.
Try
PRINT
"X";"";"X","
""
"."
""
";"";"
""
"
3. If you enjoy humiliating computers, type
PRINT
"2+2 = ";2+1

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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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