IF (e) s1,s2,s3
e Is an arithmetic expression.
s1,s2,s3 Are labels of executable statements in the same program unit. All three labels are required, but they need not refer to different statements.
Executes the statement at the first label ("s1") if the arithmetic
expression evaluates to a value less than 0; the statement at the
second label ("s2") if the arithmetic expression evaluates to 0; or
the statement at the third label ("s3") if the arithmetic
expression evaluates to a value greater than 0.
Executes the statement if the logical expression is true.
IF (e) st
e Is a logical expression.
st Is a complete Fortran statement. The statement can
be any statement except DO, END DO, END, block IF,
or another logical IF statement.
Executes a block of statements if the logical expression is true.
The block of statements starts immediately following the IF
statement. The block of statements can be followed by optional
ELSE IF statements (any number) and one optional ELSE statement.
The entire block IF construct must be terminated by an END IF
IF (e) THEN block ELSE IF (e1) THEN block ELSE block END IF
e,e1 Are logical expressions.
block Is a series of zero or more Fortran statements (called a statement block).
NOTE: No additional statement can be placed after the IF THEN statement in a block IF construct. For example, the following statement is invalid in the block IF construct:
IF (e) THEN I = J
This statement is translated as the following logical IF statement:
IF (e) THENI = J