Atari 400 User Manual

70 User's Handbook to the Atari 400/800 Computers
Note in line 910 that a GOTO statement is not used to precede
the line number being branched to . When a line number is
indicated following a THEN or ELSE statement, the computer
does not require the presence of GOTO, which is assumed.
ON, COlO Statement
The ON, GOTO statement is a combination of a conditional
statement and a branching statement. The use of the ON, GOTO
statement is illustrated in the following program.
100 INPUT A
200 ON A GOTO 250,260
210 GOTO 999
250 PRINT A: GOTO 100
260 PRINT A 1\ 2:GOTO 100
999 END
If the variable or expression following ON evaluates to 1,
program control branches to the first line number specified after
GOTO ; if 2, to the second; if 3, to the third, etc.
If the variable or expression evaluates to a number greater than
the number of line numbers following GOTO, program control
will branch to the statement immediately following the ON,
GOTO statement. This is also the case if the variable or
expression following ON evaluates to zero.
Subroutines & COSUB Statements
Many times you will find that the same set of program
instructions are used more than once in a program . Re-entering
these instructions throughout the program can be very time
consuming. By using subroutines, these additional entries will be
unnecessary.
A
subroutine can be defined as a program which appears within
another larger program. The subroutine may be executed as
many times as desired.

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)