HP 3000 Manuals HP 3000 Manuals
Writing a Program
You can write a program with any text editor or word processor. MPE/iX
provides two facilities for entering text that you can use to create a
source file for a program: Editor and Toolset/XL. For an overview of
Editor and Toolset/XL, refer to Chapter 2, "Utilities and Tools." Since
these facilities can be used for writing documents, memos, and programs,
the output is called text files. Although the source code for a program
is a text file, this guide refers to it as a source file for program
development purposes.
How to Use Intrinsics
Many programs use low-level, system supplied procedures or subroutines to
handle recurring tasks. On MPE/iX, these are performed through a set of
procedures called intrinsics, which are an integral part of the operating
system. Intrinsics are always available to any process on the system and
allow a program to gain access to system services. Tasks that intrinsics
provide include:
* Accessing and alteration of files (for example, writing to a file)
* Requesting of utility functions (for example, perform ASCII/binary
number conversion)
* Access to system resources (for example, obtain system timer
information)
You can manipulate and manage processes and system resources by means of
intrinsics, provided you have the required execution privileges. Many
intrinsics return values to the caller. Most do this through parameters;
some, through functional returns. Most intrinsics are coded in HP
Pascal/iX (one of the systems programming languages for the 900 Series HP
3000) and are defined by a procedure declaration consisting of:
* Procedure header, containing the procedure name and type,
procedure definitions, and other information about the procedure.
* Procedure body, containing executable statements and declarations
local to this procedure.
Intrinsics work like user-written procedures, except that the details of
performing the task are invisible to you.
NOTE Most intrinsics are callable from any language supported on MPE/iX.
The MPE/iX intrinsic mechanism provides flexible and convenient access to
intrinsic routines from various languages. In some programming
languages, you need not (or cannot) give descriptions for procedures that
are external to your program. When you designate that an external
routine is an intrinsic, the compiler uses the Intrinsic Mechanism to
correctly invoke the routine by:
* Providing a consistent intrinsic interface
* Ensuring proper data type conversion
* Generating proper reference parameter addresses
* Ensuring that the intrinsic is properly called
Although intrinsics usually refer to system routines, you can define
routines that you want to access as if they were intrinsics and then
place them in new or existing intrinsic files and libraries.
You invoke an intrinsic by calling it from within a program. In HP C/iX,
HP Pascal/iX, COBOL II/XL, and HP FORTRAN 77/iX programs, you explicitly
call an intrinsic. The Intrinsics Mechanism facilitates the declaration
of system intrinsics. All MPE/iX intrinsics are processed as external
procedures by user programs.
Before you can call an intrinsic from a program, you must declare it in
all languages by using an intrinsic declaration statement. The format
varies depending on the language. Refer to the appropriate language
programming guides for details on how to call intrinsics. For detailed
information on intrinsics and intrinsic declarations, refer to MPE/iX
Intrinsics Reference Manual (32650-90028).