FORTRAN Reference Manual

Statements

FORTRAN Reference Manual—528615-001

7-38

EXTERNAL Statement

The EXTERNAL statement declares the name of an external procedure and enables

you to use the name as an actual argument.

proc-name

is the name of an external procedure, dummy procedure, or block data

subprogram.

Considerations

If you use an external procedure name or dummy procedure name as an actual

argument in a program unit, you must declare it in an EXTERNAL statement in the

program unit. When you use proc-name in the argument list of a CALL statement or

function reference, FORTRAN treats it as a subprogram name rather than a variable or

array name.

If an intrinsic function name appears in an EXTERNAL statement in a program unit,

that name becomes the name of an external procedure and you cannot reference the

intrinsic function of the same name in that program unit.

Example

In the following example, the function name MULTIPLY must appear in an EXTERNAL

statement because it is used as an argument for the external function

CALC:

PROGRAM main

EXTERNAL multiply

4 p = CALC(a, b, multiply)

END

FUNCTION CALC(r,s,t)

1 CALC = s**2 + t(r)

END

EXTERNAL proc-name [, proc-name ]...