Commodore 128 Programmer's Reference Manual page 31

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BASIC BUILDING BLOCKS AND BASIC 7.0 ENCYCLOPEDIA 21
evaluating the relationship between corresponding characters from left to right (see
string operations).
EXAMPLES:
"A" < "B" result true (-1)
"X" = "YY" result false (0)
BBS <> CC$ result false (0) if they are the same
Numeric data items can only be compared (or assigned) with other numeric items.
The same is true when comparing strings; otherwise, the BASIC error message ?TYPE
MISMATCH occurs. Numeric operands are compared by first converting the values of
either or both operands from integer to floating-point form,, as necessary. Then
the relationship between the floating-point values is evaluated to give a true/false
result.
At the end of all comparisons, you get an integer regardless of the data type
of the operand (even if both are strings). Because of this, a comparison of two
operands can be used as an operand in performing calculations. The result will
be -1 or 0 and can be used as anything but a divisor, since division by zero is
illegal.
LOGICAL OPERATORS
The logical operators (AND, OR, NOT) can be used to modify the meaning of the
relational operators or to produce an arithmetic result. Logical operators can produce
results other than -1 and 0, although any nonzero result is considered true when testing
for a true/false condition.
The logical operators (sometimes called Boolean operators) also can be used to
perform logical operations on individual binary digits (bits) in two operands. But when
you're using the NOT operator, the operation is performed only on the single operand to
the right. The operands must be in the integer range of values (-32768 to + 32767)
(floating-point numbers are converted to integers) and logical operations give an integer
result.
Logical operations are performed bit-by-corresponding-bit on the two operands.
The logical AND produces a bit result of 1 only if both operand bits are 1. The logical
OR produces a bit result of 1 if either operand bit is 1. The logical NOT is the opposite
value of each bit as a single operand. In other words, "If it's NOT 1 then it is 0. If it's
NOT 0 then it is 1."
The exclusive OR IF (XOR) doesn't have a logical operator but it is performed as
part of the WAIT statement or as the XOR function. Exclusive-OR means that if the
bits of two operands are set and equal, then the result is 0; otherwise the result is 1.
Logical operations are defined by groups of statements which, when taken to
gether, constitute a Boolean "truth table" as shown in Table 2-1.