HP C/iX Reference Manual (31506-90011)

Chapter 10 175
Using Intrinsics
10 Using Intrinsics
This chapter describes the use of intrinsic functions in HP C/iX programs.
System routines on the MPE/iX operating system are generally referred to as intrinsics
because they are an integral or "intrinsic" part of the operating system. The essential
characteristic of an intrinsic is that a description of its interface is stored, in a compiled
form, in a specially formatted file known as an intrinsic file. MPE/iX intrinsics are
described in the file SYSINTR.PUB.SYS. Additionally, you can define your own intrinsics
and store their descriptions in your own intrinsic files, using the HP Pascal/iX compiler.
You use the intrinsic pragma to declare that the calling conventions for a particular
function are to be found by the compiler in an intrinsic file. You use the intrinsic_file
pragma to give the name of the intrinsic file, if it is other than SYSINTR.PUB.SYS.
An advantage of declaring a system routine as an intrinsic is that it often simplifies the
function call in the HP C source program. For example, parameters may be optional; they
can be omitted from the call and the compiler will generate the appropriate default values.
Furthermore, any "hidden" parameters required by the intrinsic will be generated
automatically. Finally, the compiler checks the types of the actual arguments against the
types of the intrinsic parameters and issues diagnostics if mismatches are found.