Intel Fortran Language Reference - NCI National Facility

Program Units and Procedures 8
The SUBROUTINE statement is the initial statement of a subroutine subprogram. It takes the
following form:
[prefix] SUBROUTINE name [([d-arg-list])]
prefix
Is one of the following:
Keyword
RECURSIVE
PURE
ELEMENTAL
Meaning
Permits direct recursion to occur. If a function is directly recursive and
array valued, RESULT must also be specified (see “Recursive
Procedures”).
Asserts that the procedure has no side effects (see “Pure Procedures”).
A restricted form of pure procedure that acts on one array element at a
time (see “Elemental Procedures”).
name
Is the name of the subroutine.
d-arg-list
Is a list of one or more dummy arguments or alternate return specifiers (*).
Rules and Behavior
A subroutine is invoked by a CALL statement or defined assignment. When a subroutine is
invoked, dummy arguments (if present) become associated with the corresponding actual
arguments specified in the call.
Execution begins with the first executable construct or statement following the SUBROUTINE
statement. Control returns to the calling program unit once the END statement (or a RETURN
statement) is executed.
A subroutine subprogram cannot contain a FUNCTION statement, a BLOCK DATA statement, a
PROGRAM statement, or another SUBROUTINE statement. ENTRY statements can be included
to provide multiple entry points to the subprogram.
Examples
The following example shows a subroutine:
Main Program
Subroutine
CALL HELLO_WORLD SUBROUTINE HELLO_WORLD
. . . PRINT *, "Hello World"
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