Data abstraction and functional and file modularization are important concepts whose proper application to program development and program structure enhance program readability and maintainability. They aid the programmer in establishing libraries of useful functions that can be readily selected for use in creating new programs for new problems.
The ability to compile parts of a program separately can make debugging an easier task and can save time. In C this can be achieved by placing appropriate parts of a program in distinct files. When this is done it is necessary to keep track of which files must be compiled and linked in order to execute the program file.