Atari 800 User Manual

90 User's Handbook to the Atari 400/ 800 Computers
response other than that prompted for.
The very
nature of the Input statement prevents certain errors
from occurring as these are detected by the BASIC interpreter .
For
example, if a numeric entry is made when a string variable is
specified with the I nput statement, an error will occur. Li kewise,
if a string entry is made when a numeric variable is specified with
the Input statement, an error will occur.
However , many Input entry errors will not be detected by the
BASIC interpreter. Serious errors can occur when the wrong
data is entered in response to an Input statement. It is a good
programming practice to check the operator's response to an
Input statement. This can either be accomplished with one or
more IF-THEN statements, or with ON-GOTO or ON-GOSUB
statements.
For
example, in the following program , the operator's input is
checked with two IF-THEN statements. If the response is neither
of the following,
Y, N, y, n
the program will branch back to line 1200 for a new entry.
1000 DIM A$(20)
1100 PRINT
1200 PRINT "Enter Your
Response (Y I N)"
1300 INPUT A$
1400 A$ = A$(1 , 1)
1500 IF A$ = " Y" OR A$ = "y" THEN 1800
1600 IF A$ = "N" OR A$ = "n" THEN 9999
1700 GOTO 1300
1800 REM Subroutine For 'Yes' Response
1900 PRINT "YES"
9999 END

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