5 Operators and Functions

Relational Operators

The relational operators are:

Operators	Operations	Examples
<	less than	A < B
>	greater than	A > B
<=	less than or equal to	A <= B
>=	greater than or equal to	A >= B
=	equals	A = B
<> or #	not equal to	A <> B

When relational operators are used in a numeric expression, the value 1 is returned if the relation is found to be true; the value 0 is returned if the relation is false. For instance, A=B is evaluated as 1 if A and B are equal in value, 0 if they are not equal. If A=1, B=2, and C=3, then (A*B)<(A-C/6) is evaluated as 0 (false) because A times B equals 2, which is not less than 0.5 (the result of (A-C/6)).

Here is a sample program:

10   INPUT "ENTER THREE VALUES:";A,B,C
20   Logic=(A*B<C)
30   If Logic THEN
40       PRINT "(A*B<C) is TRUE and has a value of ";Logic
50   ELSE
60       PRINT "(A*B<C) is FALSE and has a value of ";Logic
70   END IF
80   END

(A*B<C) is FALSE and has a value of 0

Relational operators are also used to compare strings. Strings are compared according to their associated numeric values in the ASCII code (see page 391 ). The strings are compared character-by-character until a difference is found or until the end of a string is reached. If the ends of both strings are found at the same time, the strings are equal. If the end of one string is reached first, however, then that string is an initial substring of the other, and is considered to be less than the longer string. For example, all the following expressions are true:

"AB" < "ABC"   "AB" is an initial substring of "ABC".

"AB" = "AB"     Both strings are exactly equal.

"B" > "ABC"  "B" has a higher numeric equivalent than "A" in the ASCII code.

"AB$" < "AB*" "$" has a lower numeric equivalent than "*" in the ASCII code.