Atari 800 User Manual

Alari BASIC Reference Guide 117
A FOR/NEXT loop can use a STEP statement to increment the
counter by a value other than 1.
EXAMPLE
10 FOR J = 1 TO 2 STEP .5
20 PRINT L
30 NEXT J
RUN
1 1.5 2
The preceding example contains a FOR/ NEXT loop which
increments the value of J by .5 each time the loop is executed.
A
FOR / NEXT loop can also be used to decrease the value of the
counter. This can be accomplished by using the optional STEP
statement within the FOR statement. If the STEP statement has a
negative
argument, the counter is decreased each time the loop
is executed. The following example illustrates a FOR/NEXT loop
where the counter is decremented rather than incremented .
EXAMPLE
10 FOR K = 10 TO 5 STEP -2
20 PRINTK ,
30 NEXT K
RUN
10 8 6
This loop begins at line 10 by assigning the counter (K) the value
10. At line 20 the value of K is printed. When line 30 is
encountered, execution continues at line 10 , because the NEXT
statement returns the program to the preceding FOR statement.
The
value of the counter is changed by the argument of STEP.
Since the STEP value is -2 , the counter is decreased by 2. The
value of the counter is changed to 8. At line 20, the new value of
K is printed. Line 30 is executed again, so the program returns to
the FOR statement at line 10 . The counter is again decremented
by 2. The new value of K is 6. At line 20, this K value is printed.
When line 30 is executed again, the program does not return to

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