Functions, subroutines, and statement functions are user-written subprograms that perform computing procedures. The computing procedure can be either a series of arithmetic operations or a series of Fortran statements. A single subprogram can perform a computing procedure in several places in a program, to avoid duplicating a series of operations or statements in each place.
The following table shows the statements that define these subprograms, and how control is transferred to the subprogram:
|Subprogram||Defining Statements||Control Transfer Method|
|Function||FUNCTION or ENTRY||Function reference 1|
|Subroutine||SUBROUTINE or ENTRY||CALL statement 2|
|Statement function||Statement function definition||Function reference|
1 A function can also be invoked by a defined operation
(see Section 8.9.4).
2 A subroutine can also be invoked by a defined assignment (see Section 8.9.5).
A function reference is used in an expression to invoke a function; it consists of the function name and its actual arguments. The function reference returns a value to the calling expression that is used to evaluate the expression.
The following topics are described in this section:
For More Information: