Library (computing): Difference between revisions

Revision as of 21:52, 12 July 2004

Revision as of 03:16, 27 July 2004

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== Shared library ==

Libraries can be linked dynamically. In [[Microsoft Windows]], those are called '''dynamicallydynamic linked librarylibraries''', or '''DLLDLLs'''. Conventional libraries are often called static library to distinguish from shared libraries.

The shared library term is slightly ambiguous, because it covers at least two different concepts. First, it is the sharing of code located on disk by unrelated programs. The second concept is the sharing of code in memory, when programs execute the same physical page of RAM, mapped into different address spaces. RAM sharing can be accomplished by using [[position independent code]] as in [[Unix]], which leads to a complex but flexible architecture, or by using normal, ie. not position independent code like in [[Microsoft Windows]] and [[OS/2]], but making sure, by various tricks like pre-mapping the address space and reserving slots for each DLL, that code has a great probability of being shared. Windows DLLs are not shared libraries in the Unix sense. The rest of this article concentrates on aspects common to both variants.