The EXTPGM keyword indicates
that the prototype
represents a dynamic call to a program.
The parameter specifies the external name of the program whose prototype
is being defined. The name can be a character constant or a character variable.
The parameter is optional
if the prototype name is not longer than 10 characters.
If the parameter is not specified, the external program
name is the same as the upper-case form of the prototype name.
The following example defines a prototype for program 'QCMDEXC'.
DCL-PR qcmdExc EXTPGM;
...If neither EXTPGM or EXTPROC is specified for a prototype, then the
compiler assumes that
you are defining a prototype for a procedure, and assigns the
external procedure name to be the upper-case form of the
prototype name.
Any parameters defined by a prototype or procedure interface with EXTPGM must be passed by reference. In addition, you cannot define a return value.