C is built on a foundation of functions--both those functions that you write and the func tions supplied by C. The next two sections should help you understand the nature of C functions.
Using Built-In Functions
Unlike just about every other programming language in the world, C has no input or out put statements. Look through Table 13.1 once more. You don't see a Print statement or anything else that might be considered an I/O statement.
C performs all its I/O through functions that your C compiler provides. By letting the compiler makers implement I/O in functions, the C language is highly portable , meaning that a C program that runs on one kind of computer should run on any other computer than is capable of running C programs. ...