Atari 800 User Manual

52 User's Handbook to the Atari 4001800 Computers
Compound Expressions and Order of Evaluation
All of our preceding examp l es were simple expressions. A simple
express ion is one which conta ins just one operator and one or
two operands. Simple expressions can be combined to form
compound expressions. The following are examples of
compound expressions.
(A + B) * 7- 4
(A + B) AND (C +D)
IF A = 1 AND B = 1 THEN C = 1
With compound expressions, it is necessary that the computer
knows which operat ion should be undertaken first. Atari BASIC
follows a standard order or evalu ation within compo und
expressions. This order is out lin ed in Table 3-1.
Note that parentheses have the highest precedence level. In
other words, any expressi on enclosed within parentheses will be
evaluated first. If more than one set of parentheses appears in an
expression, these
will be evaluated from l eft to right.
One pair of parentheses can be used to enclose an operator
enclosed within another set. In such an instance, Atari BASIC will
eva luate the expression within the innermost set of parentheses
first,
followed by the next innermost set, etc.
When expressions have the same order of evaluation , they wil l
be evaluated in order from left to right w ithin the compo und
exp ression .

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