Atari 800 User Manual

Atari BASIC Reference Guide 93
The conditions of true and false are represented in the computer
by the logical values 1 and O. As a result, the logical operators
(AND , OR, and NOT) generate only the values 1 and o. The AND
operation can be explained by the following truth table.
EX1
1
1
o
o
EX2
1
o
1
o
RESULT
1
o
o
o
AND is generally used in an IF / THEN statement with relational
expressions. For example:
10 X = 10
20 Y = 30
30 IF X = 10 AND Y>100 THEN END
40 PRINT "CONDITIONS WERE NOT MET"
RUN
CONDITIONS WERE NOT MET
In this example, AND is us ed in an IF / THEN statement which
ends the program if both co nditions are true . The first expression
of the AND statement is X =10. This is true because X is assigned
the
value 10 in line 10. The second expression, Y>100 , is false
because Y is assigned the value 30 in line 20. As a result, EX1 is true
and EX2 is false. This corresponds to the truth table where EX1 = 1
and
EX2 = O. The resu It from the table is 0 (fa Ise) , so the cond ition
of the IF / THEN statement is false, and the next line is executed.
The
AND operator can also be us ed with algebraic expressions
like 5 * Y, 3 + X, X II 2, etc. However , these must also be converted
to logical 0 or 1. The computer does this by assigning the logical
value 0
to any express ion that equals O. Any expression that does
not equal 0 is assigned the logical value 1. For example , the
logical value of 5 * 0 is O. The logi ca l values of 3 + 1, 2 II 2,3 and
COS (45) are all 1.

Atari 800 Specifications

General

Processor	MOS Technology 6502
Processor Speed	1.79 MHz
ROM	10 KB
Graphics	ANTIC and GTIA chips
Release Year	1979
Display Resolution	up to 320 x 192
Colors	128 colors
Sound	4 channels
Storage	Cartridge, cassette, floppy disk
Ports	Cartridge, serial, monitor
Operating System	Atari OS