Turbo Basic

Relational OperatorsRelational operators allow you to compare the values of two strings or two numbers(but not one of each) to obtain a Boolean result of TRUE or FALSE. The result ofthe comparison is assigned an integer value of - 1 if the relation is TRUE, and 0 ifthe relation is FALSE. For example:PRINT 5 > 6, 5 < 6, (5 < 6) * 15prints out 0, - 1, and - 15. Although they can be used in any numeric expression(for example, a = (b > c) / 13), the numeric results returned by relational operatorsare generally used in an IF or other decision statement to make a judgmentregarding program flow. Table 4-3 lists the relational operators.Table 4-3Relational OperatorsOperator Relation ExampleEqualityx = y Inequality xy< Less than x < y> Greater than x > y=yWhen arithmetic and relational operators are combined in an expression, arithmeticoperations are always evaluated first. For example, 4 + 5 < 4 * 3 evaluatesto -1 (TRUE), because the arithmetic operations are carried out before the relationaloperation, which ultimately tests the truth of the assertion: 9 < 12.Logical OperatorsLogical operators perform logical (Boolean) operations on integers. Used with relationaloperators, they allow you to set up complex tests likeIF day> 29 AND month = 2 THEN PRINT "Error in date"This statement performs a logical AND on the integer results returned by thetwo relational operators. (The AND operator has a lower priority than the " > " and"=" relational operators, so parentheses aren't needed.) For example, if day = 30and month = 2, both relational operators return TRUE (- 1). The underlyingbinary representation of integers is such that - 1 has a value of &HFFFF (all bitsturned on); 0 is &HOOOO, all bits turned off.The AND operator then performs a logical AND on these two TRUE results:1111 1111 1111 1111 (-1)AND 1111 1111 1111 1111 (-1)1111 1111 1111 1111 (-1)producing a TRUE (nonzero) result.Turbo Basic: The Language 79