Atari 400 User Manual

In troduction to Atari B AS IC 55
Relational Operators
The follo w in g rela tional operato rs are us ed in Atari BASIC.
<
<=
>
>=
------- ~~ I ess than
------...., .~ l ess than o r eq ual to
------....,~ ~ greate r than
------...., .~ greate r than or eq ual to
-------l.~ eq u a I to
<> ------...., .~ not e qual
A relational opera ti on evaluates to eit her true or false. For
exa mple , if the constant 1.0 was co mp ar ed to the constant 2. 0 to
see whether they we re eq ual, the expr ess ion would eva luate to
false. In Atari BASIC, a va lu e of 1 repr esents a co ndition of true ,
while a va lu e of 0 repr ese nt s fa l se.
The only values r et urn ed by a co mp ari so n in BASIC are 1 (true)
o r 0 (false). Th ese va lu es ca n be used as any other int eger would
be us ed . The following resu l ts are ge nerat ed by the following
re lational expressions.
5>7 ........... 0 (false)
3 = 3 - 1 (true)
2<>2 - 0 (false)
(2=2)*4-4
( 1) 7)+7 -7
The first thr ee exa mpl es are easy enoug h to und ersta nd . In the
fourth example , the relation al ex pr ess ion (2 = 2) is eva lu at ed first
as tru e or 1. This r es ult is then multiplied by 4 with a product of 4
as the result. In the fifth exa mple, the relational expression (1 >
7) eva lu ates as false o r O. This res ult is added to 7, with the res ult
being 7.
Relat ion al ope rations using num e ric opera tio ns are fa irly
s tr a ightforw ard. H owever , relational operatio ns us ing string
values may prov e co nfusing to the first-time co mput er user.

Atari 400 Specifications

General

Manufacturer	Atari
Model	400
Type	Home Computer
Release Year	1979
CPU	MOS Technology 6502
CPU Speed	1.79 MHz
ROM	10 KB
Operating System	Atari OS
Keyboard	Membrane keyboard
RAM	8 KB (expandable to 48 KB)
Graphics	ANTIC and GTIA chips
Sound	4 channels
Display	RF output for connection to TV
Storage	Optional cassette tape drive or floppy disk drive
Ports	Cartridge
Display Resolution	320x192 (16 colors)