Commodore PET - Writing BASIC Programs

Since no previous program has the character 4 in it. PGM 4 will be loaded.
Because of the character-by-character search for file name matches. vou have to
be careful when giving abbreviated names. especially if your file names are long.
For example. suppose vou save three programs successively
as:
WHILE AWAY THE HOURS
WHILE A
WHILE B
Vou
will not be able to load the second program with a LOAD "WHILE A" com-
mand. The first program
would always be loaded. since it contains that character
subgroup.
There
is something else vou must bear in mind when vou make up file names.
Although the file name may have up to 128 characters. only the first 16
characters are displayed by the PET. If vou save two programs successively as:
SWEET SIXTEEN TEST 1
SWEET
SIXTEEN TEST 2
the programs are subsequently listed
as:
SWEET SIXTEEN TE
SWEET SIXTEEN TE
so vou can't tell which is which by examining file names as they are displayed.
ln summary. vou
will find it helpful to compose file names using 16 characters or
less. and vou should keep file names about the same length.
WRITING BASIC PROGRAMS
A BASIC program consists of a group of numbered statements. In con-
trast to immediate mode. statements within a program are not executed un-
til
vou "run" the program. In other words. when vou type in program state-
ments. nothing happens until vou specifically initiate program execution.
When a
statement begins
with a line number, PET BASIC stores the statement rather than
executing
it immediately. Aline number is put on a statement to indicate that it is
part of a stored program.
L1NE NUMBERS
Every program statement begins with a line number that must be
unique within the program and therefore uniquely identifies the statement.
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