The general form for the IF statement is:
For example the statement:
makes x positive.
Logical expressions can be stored as LOGICAL variables.
IF statements can be nested within one of the flow control constructs but not vice-versa.
Unlike flow control constructs, an IF statement can not be named.
For most purposes, an IF construct is preferred to an IF statement, even in simple cases. For example,
though less concise, scans more easily. The IF statement may, however, be preferred for use with the statements STOP, RETURN, EXIT and CYCLE.