iTS 1.0+)

SCREEN COBOL Source Program

Compaq NonStop™ Pathway/iTS SCREEN COBOL Reference Manual—426750-001

2-18

Conditional Expressions

Example 3

In the following example, with either of the following:

COMPUTE AX = A1/A2 + A3 * A4.

IF A1/A2 + A3 * A4 LESS THAN AX GO TO ...

the division is performed before further evaluation of either of the above statements.

The intermediate result is then adjusted to fit the conceptual PICTURE derived by

examining the other operands in the expression.

Incompatible Data

An incompatible data condition occurs when a data item is referenced by a statement in

the Procedure Division and that item contains characters not permitted by the statement.

For example, if a position in a display numeric item contains an alphabetic character, A,

and that item is used as an operand in an ADD statement, an incompatible data condition

occurs. The result of this reference is undefined.

The class condition test is an exception to this rule because its purpose is to determine

whether or not items contain legal data.

Conditional Expressions

Conditional expressions identify conditions that are tested by the program to select

between alternate paths of control. Conditional expressions are specified in the IF and

PERFORM statements.

The two categories of conditions for conditional expressions are: simple conditions and

complex conditions. Either kind of condition can be enclosed within any number of

paired parentheses without changing the category of the condition.

Simple Conditions

Simple conditions are of four kinds:

•

Class conditions

•

Condition-name conditions

•

Relation conditions

•

Sign conditions

Simple conditions have a truth value of true or false. Parentheses can enclose a simple

condition without changing the truth value of the condition.