Atari XL User Manual

46
The Afar; XL Handbook
This method of entering information is much easier
to use than simply writing it into the program by
setting variables. Imagine the typing involved in
entering lots of lines like:
PRICE(2)=5.75
With DATA lines you can layout the information
in a clear tabular form and check it much more
easily. You can also alter it if you need to without
touching the main program.
When a program is running, the computer uses a
'pointer' stored in its memory to keep track of how
many DATA items it has read. Every time a
READ command is met, the DATA item indicated
by the pointer is copied into the variable, and the
pointer moves on to the next item. This means you
must have a DATA entry corresponding to each
occurrence of READ. The program will stop if
there are too many READ commands and the
Atari will print an error message: ERROR-6.
The command RE STO RE can be used to reset the
data pointer to the first DATA item in the
program. RESTORE followed by a line number,
such as:
50 RESTORE 2000
will reset the data pointer to the first DA l' A item
which occurs after that line.
The variables used in the READ command must
match the type of data in the corresponding DATA
entry. A READ with a string variable will read
anything as a string, but READ with a number
variable must find a number in the DATA entry or
the error message ERROR-6 will result.

Atari XL Specifications

General

Release Year	1983
CPU	MOS Technology 6502C
Graphics	ANTIC, GTIA
Sound	POKEY (4 channels)
Storage	Cassette tape
Ports	Cartridge
Operating System	Atari BASIC
CPU Speed	1.79 MHz
RAM	64 KB