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TBASIC.B2
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1984-04-29
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<variable list>
A sequence of variable names, seperated by commas or semicolons.
<logical constant>
A constant which has the value of either -1 (true) or 0 (false).
Notice that in some systems, any integer other than zero is
considered true. This can produce an ambiguity, however, in
that a NOT TRUE operation could produce a TRUE value.
<logical operator>
AND, OR, and NOT are the logical operators. When the AND
operator is between two logical constants, the combination
is true if both values are true. When the OR operator is
between two logical expressions, the combination is
true if either value is true. When the NOT operator is
before a logical expression, the combination produces a TRUE
value if the expression were FALSE, and a FALSE value if the
expression were TRUE. The logical operators all perform
as if they were operating on each bit of a 16-bit
binary number, with all bits operated on in parallel.
Examples: 2 AND 3 produces 3
1 OR 4 produces 5
NOT 0 produces -1
<logical variable>
A variable whose value is either -1 (true) or 0 (false).
<logical expression>
An expression which evaluates to either a -1 (true) or 0 (false).
Examples:
LET TRUE=-1:LET FALSE=0
TRUE AND TRUE produces TRUE
TRUE AND FALSE produces FALSE
FALSE AND TRUE produces FALSE
FALSE AND FALSE produces FALSE
TRUE OR TRUE produces TRUE
TRUE OR FALSE produces TRUE
FALSE OR TRUE produces TRUE
FALSE OR FALSE produces FALSE
NOT TRUE produces FALSE
NOT FALSE produces TRUE
<line descriptor>
A sequence of numerals and letters (not punctuation), which
starts with the first character position (left-hand margin)
in a TARBELL BASIC statement line, and which is terminated
by either a space or a tab (ctl-I), and which is not one of
the reserved words in Appendix H. If the descriptor is in
a statement referencing another statement, a + or - offset
may be included.
<line descriptor list>
A sequence of line descriptors, seperated by commas.
B-2