z/TPF Program Management - IBM

z/TPF program types and linkage
An object file is a compiler or assembler output file that is suitable as input to a
linkage editor. In the z/TPF system, object files are included in a shared object,
which is all or part of a computer program in a form suitable for loading into main
storage for execution. A shared object usually is the output of a linker. Depending
on the z/TPF program, there are different ways to package programs for linkage.
The number of entry points defined impacts the way these programs are
externalized to other programs for linkage. There are a number of ways to increase
the efficiency of the linkage between these programs and to improve the
performance of your z/TPF system.
A BAL shared object (BSO) is a type of shared object consisting of one or more
objects that are created by assembling z/TPF E-type basic assembler language
(BAL) programs. By contrast, a C shared object (CSO) is a type of shared object
consisting of one or more objects that are created by compiling C language
programs or assembling z/TPF BAL programs using C/C++ calling conventions.
Both BSOs and CSOs can have single and multiple entry points. See z/TPF
Application Programming for more information.
Figure 1 shows E-type program types in the z/TPF system.
BAL shared object (BSO)
Single entry point
CSO program without
the main function
Figure 1. E-type program types
E-type programs / shared objects
Single entry point
CSO program with
the main function
Assembler and C program packaging
C shared object (CSO)
Library
(non-program)
Program and library
BSOs and CSOs can be repackaged into multiple entry point shared object libraries
to provide the following performance advantages and benefits:
v Reduction in system overhead for an application because two segments can be
linked together as one unit, creating a shorter path length because internal
linkage paths are faster than external paths.
v For BSOs:
– Program expansion beyond 4 KB.
– The program can be coded with multiple base registers or can remain
baseless.
– The assembler API of R0 - R7 has been expanded to include R8.
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