Commodore CBM - PET Key Groups

Variables
Under some circumstances the BASIC interpreter will treat a keystroke as
part of a BASIC statement. Or the keystroke may become part of a "symbol" or
variable name.
We use the word "syntax" to describe the rules governing the
form that BASIC statements must have and the way characters
within the BASIC
statement
will be interpreted.
7T is a "symbol"; it represents the value 3.14159265, the circumference of a
circle divided by its radius.
The concept of a
"symbol" or "variable" is fundamental to ail computer pro-
grams,
whether they are written in BASIC or in any other programming language.
You create variable names by grouping letters
and/or other characters, according
to specified rules. Each variable becomes an entity, capable of representing infor-
mation. The information may
be a number or a word of text. You may liken varia-
bles to letter boxes, each of
which has a na me, but can contain whatever vou
choose to
put into it.
The information represented by a variable name may
be a string of text. an
integer, or a floating point (real) number. If the last character of the variable na me
is %, the variable can represent only integers. If the last character of the label is $,
the label can represent only strings. If the last character of the label is neither %
nor $, then the label can represent only floating point numbers.
Until a program assigns a value to a variable
na me, the variable is assumed
to have a value of 0 for a number, or no characters at ail for a string.
PET KEY GROUPS
The PET keys can be divided into the following groups:
Alphabetic keys
Numeric keys
Special symbols
Graphie keys
Function keys
Cursor control keys
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