DLL concepts and terms

Function: In this chapter, function is used to generically refer to a callable routine or program, and is specifically applicable to C and C++.
Variable: In this chapter, variable is used to generically refer to a data item, such as a static variable in C/C++.
Application: All the code executed from the time an AMODE 64 executable program is invoked until that program, and any programs it directly or indirectly calls, is terminated.
DLL: An executable module that exports functions, variable definitions, or both, to other DLLs or DLL applications. The executable code and data are bound to the program at run time. The code and data in a DLL can be shared by several DLL applications simultaneously.
DLL application: An application that references imported functions, imported variables, or both, from other DLLs.
Executable program (or executable module): A file which can be loaded and executed on the computer. For AMODE 64 applications, z/OS only supports program objects created by the binder that reside in either a PDSE or in the HFS.
Object code (or object module): A file output from a compiler after processing a source code module, which can subsequently be used to build an AMODE 64 executable program module.
Source code (or source module): A file containing a program written in a programming language.
Imported functions and variables: Functions and variables that are not defined in the executable module where the reference is made, but are defined in a referenced DLL.
Non-imported functions and variables: Functions and variables that are defined in the same executable module where a reference to them is made.
Exported functions or variables: Functions or variables that are defined in one executable module and can be referenced from another executable module. When an exported function or variable is referenced within the executable module that defines it, the exported function or variable is also nonimported.
Writable Static Area (WSA): An area of memory that is modifiable during program execution. Typically, this area contains global variables and function and variable descriptors for DLLs. The environment supplied to an XPLINK function (in register 5) is the part of WSA that is applicable to that function.
Function descriptor: An internal control block containing information needed by compiled code to call a function.