## If (arithmetic)

### Statement Type:

An arithmetic IF is an executable branching statement. It is a very arachic structure in
Fortran and could be removed from a future Fortran standard. Therefore, you should
**never use this in any new programs that you write.
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### Statement Purpose:

In ancient Fortran, the Arithmetic IF provided a way for Fortran to branch to different
program statements based upon the evaluation of an arithmetic expression that followed
the if statement. This function has been superseded by the present capabilities of Fortran
and the **arithmetic if should never be used in any program you write.**

### Additional Required Statements:

if ( mathematical expression ) label number, label number, label number

The mathematical expression is first evaluated and its value is determined. Now, if the
expression evaluates to be less than zero the program will branch to the first label number
that follows the mathematical expression. If the expression evaluated to be equal to zero,
then the program would branch to the second label number following the expression.
Finally, if the expression evaluated to be greater than zero, then the program would
branch to the last of the label numbers.

### Examples:

The following is what an arithmetic if looks like. **Remember, avoid using this
structure in any programs you write.** The only reason why it is introduced is to show
you what one looks like just in case you run into one when modifying an earlier Fortran
program. The structure looks like the following.

If (b**2-4*a*c) 100,200,300,
100 print*, 'Roots are complex'
Go to 400
200 print *, ' single real root '
Go to 400
300 print *, 'two real roots'
400 continue

In this type of structure the program branches to label 100 if the arithmetic expression in
parenthesis evaluates to less than zero, or to 200 if it evaluates to be equal to zero or
would branch to 300 if it evaluates to greater than zero.

### Related Topics and Lectures:

lecture eleven

block if

Logical if

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Written by Jason Wehr : jcw142@psu.edu and Maintained by John Mahaffy :
jhm@cac.psu.edu