ABSTRACT
In any software development organization, multiple projects are executed and some functionalities are repeated across projects. Of course, we can copy and paste the code from one project to another, but it is a better practice to write subroutines and reuse them in different projects as required. Computers provide a facility of building libraries with subroutines whose functionalities can be useful in multiple projects. Libraries are of three kinds, namely, the static libraries, dynamic link libraries, and shared libraries. Static libraries are those sets of subroutines whose code will be attached to the executable program at the stage of linking the object code with the libraries. Dynamic link libraries do not attach the code to the executable code but are loaded into the RAM during run time of the program as required. Shared libraries are those whose code resides in the RAM and becomes available to any program running on the computer. To build a library, we need to compile the selected subroutines into object code using the special facility available for this purpose. Then, using the command available in the OS, we build all such object code into a library. The facilities for building libraries can differ from OS to OS. We need to learn them to build the libraries. If we build the libraries carefully, it has the tremendous possibility to reduce coding effort and improve the quality at the same time All programmers ought to master the skills to build and use the reusable code libraries. All these aspects are discussed in this chapter.
