A sequence of variable names, seperated by commas or semicolons. 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. 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 A variable whose value is either -1 (true) or 0 (false). 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 A sequence of s, 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. A sequence of line descriptors, seperated by commas. B-3