Atari 800 User Manual

Atari BASIC Reference Guide 127
The expression (EX) that follows IF can be logical or algebraic.
Any algebraic expression that does not equal zero is considered
true. The logical operators (AND, NOT and OR) can be used in
the IF expression.
10 X = 15
20 Y = 30
EXAMPLE
30 IF X>10 AND Y>20 THEN 50
40 PRINT "CONDITIONS NOT MET":END
50 PRINT "CONDITIONS HAVE BEEN MET"
RUN
CONDITIONS HAVE BEEN MET
The previous
example shows two logical expressions and a
logical operator in the IF / THEN statement (line 30). The AND will
only be true when both conditions have been met. Since X = 15
(line 10) and Y = 30 (line 20), both of the conditions of line 30 are
true.
As a result, the program branches to line 50. At line 50, the
message CONDITIONS HAVE BEEN MET is printed.
An END statement is used in line 40 to prevent both messages
from being printed when the IF statement is false.
An IF/THEN statement can also be followed by statements
instead
of a line number.
10 Y = 5
20 X = 10
EXAMPLE
30 IF X<100 THEN PRINT X:PRINT Y
RUN
10
5
The previous example shows that statements can follow a THEN
statement, separated
by colons. If the condition is true, the
statements are executed.
If the condition is false, the program
will continue at the next line , and the statements after the THEN
statement are
ignored . Si nce X = 10 (line 20), the condition at line

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