Open Watcom FORTRAN 77 Language Reference

Language Reference
2.50 Arithmetic IF Statement
IF (e) s1, s2, s3
where:
e
is an integer, real, or double precision expression.
s1, s2, s3 are statement labels of executable statements that appear in the same program unit
as the arithmetic IF statement.
The expression e is evaluated and if the value is less than zero then transfer is made to the statement
identified by label s1. If the value is equal to zero then transfer is made to the statement identified by
label s2. If the value is greater than zero then transfer is made to the statement identified by label s3.
Example:
IF( SIN( X ) ) 10, 20, 30
10 PRINT *, ’SIN(X) IS < 0’
GO TO 40
20 PRINT *, ’SIN(X) = 0’
GO TO 40
30 PRINT *, ’SIN(X) > 0’
40 CONTINUE
The above example evaluates the sine of the real variable X and prints whether the result is less than 0,
equal to 0, or greater than 0.
The same label may appear more than once in the arithmetic IF statement.
Example:
IF( SIN( X ) ) 10, 10, 30
10 PRINT *, ’SIN(X) IS 0’
40 CONTINUE
The above example evaluates the sine of the real variable X and prints whether the result is less than or
equal to zero, or that it is greater than 0.
84 Arithmetic IF Statement