Logical

 Executes the statement if the logical expression is true.  In
 Fortran 95/90, this is called an IF statement (as compared to block
 IFs, which are called IF constructs).  Statement format:

    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, 
        CASE, FORALL, or WHERE constructs, or another logical 
        IF statement.