Commodore VIC-20 - Operators

The three Boolean operators can also be used to perform logic
operations on the individual binary digits of two adjacent terms (or
just the term to the right in the case of NOT). But the terms must be
in the integer range. Boolean operations are defined by groups of
statements, which taken together constitute a "truth table." The
following table lists the truth tables for the Boolean operators used
by VIC BASIC.
I
Boolean Truth Table
The AND operation results in a 1 only if both bits are 1.
1 AND 1 = 1
0 AND 1 = 0
1 AND 0-0
0 AND 0 = 0
The OR operation results in a 1 if either bit is 1.
1 OR 1 =1
0 OR 1 = 1
1 OR 0 = 1
0 OR 0 = 0
The NOT operation logically complements each bit.
NOT 1 = 0
NOT 0 = 1
I
Thisdiscussion of binary digit (bit) oriented Boolean operations is
presented for those who are interested in the details of how these
operations are performed. If you do not understand it, skip it. You
are not skipping anything you must know. Recall that a single term
has an implied "<>0" following it. The expression therefore
becomes:
IF G<>0 GOTO 40
Thus, the branch is not taken.
In contrast, a Boolean operation performed on two variables may
yield any integer number:
IF A% AND B% GOTO 40
Assume that A% = 255 and B% = 240. The Boolean operation 255
AND 240 yields 240. The statement, therefore, is equivalent to:
66
I