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In IBM System/360 through IBM Z mainframe operating systems such as OS/360 and its successors, this type of program is known as a linkage editor. As the name implies a linkage editor has the additional capability of allowing the addition, replacement, and/or deletion of individual program sections. Operating systems such as OS/360 have format ...
The program had to explicitly call the CHAIN subroutine to load a new link, and the new link replaced all of the old link's storage except for the Fortran COMMON area. IBM introduced more general overlay handling [ 7 ] in IBSYS / IBJOB , including a tree structure and automatic loading of links as part of CALL processing.
An example of load-and-go systems is the loader Anthony J. Barr wrote for the University Computing Corporation in 1968 that was replaced in the market by the IBM OS/360 loader in 1972. These OS/360 loaders performed many of the functions of the Linkage Editor but placed the linked program in memory rather than creating an executable on disk. [9]
In OS/360 and descendant systems, the (privileged) operating system facility is called IEWFETCH, [2] and is an internal component of the OS Supervisor, whereas the (non-privileged) LOADER application can perform many of the same functions, plus those of the Linkage Editor, and is entirely external to the OS Supervisor (although it certainly ...
Linking is often referred to as a process that is performed when the executable is compiled, while a dynamic linker is a special part of an operating system that loads external shared libraries into a running process and then binds those shared libraries dynamically to the running process. This approach is also called dynamic linking or late ...
Any static library function can call a function or procedure in another static library. The linker and loader handle this the same way as for kinds of other object files. Static library files may be linked at run time by a linking loader (e.g., the X11 module loader). However, whether such a process can be called static linking is controversial.
Relocation is the process of assigning load addresses for position-dependent code and data of a program and adjusting the code and data to reflect the assigned addresses. [1] [2] Prior to the advent of multiprocess systems, and still in many embedded systems, the addresses for objects are absolute starting at a known location, often zero.
The handling of DLLs in Windows differs from the earlier OS/2 procedure it derives from. OS/2 presents a third alternative and attempts to load DLLs that are not position-independent into a dedicated "shared arena" in memory, and maps them once they are loaded. All users of the DLL are able to use the same in-memory copy.