What are Libraries ?

A library is a file that contains a collection of object (compiler output) files together with an index to permit direct access to each of the component files. Libraries simplify the process of linking (see section 6.1.4); instead of listing every individual object file, which could run into hundreds or even thousands of files, you instruct the linker to build the program from a relatively few libraries. Furthermore, the linker only takes from a library those files that it needs. Libraries represent the large scale structure of a software project. Third party software suppliers who provide component software, e.g. a graphics package, will do so in terms of one or more libraries. Then when you link your program the linker will only load those parts of those libraries that you need.