Commodore PET User Manual page 30

Special Symbols
Special symbols, or special characters, have two general uses:
1.
They may represent standard punctuation marks or commonly used
symbols. For example, there is a period, a comma, arithmetic opera-
tions (+ for addition. - for subtraction. etc.). and other characters that
have widely recognized interpretations, such as "$" for dollar sign.
2. These same characters may at other times represent a specifie opera-
tion or be part of a BASIC statement. Remember, we use the word
"syntax" to describe the special rules governing the characters that
must appear in a BASIC statement and the order in which they must ap-
pear.
Thus, the same symbol means different things when used in different
contexts. Some English words. called homonyms, also have this property. For ex-
ample. pool can be a pool of water or a game of pool.
Consider the following PET BASIC statement:
IF A=l THEN B=2
This BASIC statement uses the equal sign (=) twice, apparently with the
same meaning in each case. But these two equal signs actually mean different
things to PET BASIC. The first equal sign. in the phrase IF A=l. has a standard
meaning of equality; PET BASIC must determine whether A has the current value
of 1. In the second phrase. THEN B=2, however, the equal sign in interpreted as
"assign B the value of 2. regardless of what its current value is." These equal
signs are called "program operators." A program operator is a special symbol that
tells PET BASIC to perform a certain operation.
Note that "A" and "B" have been used as var·iables; each is a "name"
assigned to a ''1etter box." The BASIC statement above checks to see if letter box
"A" contains 1; if it does, 2 gets put into letter box "B".
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