IF-THEN-ELSE-END IF

The most general form of the IF-THEN-ELSE-END IF statement is the following:

IF (logical-expression) THEN
   statements-1
ELSE
   statements-2
END IF
where statements-1 and statements-2 are sequences of executable statements, and logical-expression is a logical expression. The execution of this IF-THEN-ELSE-END IF statement goes as follows:

Examples

A Useful Tip

You may find the following way of organizing IF-THEN-ELSE-END IF very useful, especially when your program logic is reasonably complex.

Draw a rectangular box and a vertical line dividing the box into two parts. Then, write down the logical expression in the left part and draw a horizontal line dividing the right parts into two smaller ones. The upper rectangle is filled with what you want to do when the logical expression is .TRUE., while the lower rectangle is filled with what you want to do when the logical expression is .FALSE.:

logical-expression what you want to do when the logical expression is .TRUE.
what you want to do when the logical expression is .FALSE.

For example, the third example above has the following description:

a <= b a is the smaller number
b is the smaller number

Although this is an easy example, you will sense its power when you will be dealing with more complex problems.