UNIX supplies a standard package for performing buffered input and output to files or the terminal. This contains most of the functions which will be introduced in this section, along with definitions of the datatypes required to use them. To use these facilities, you should include their definitions in your program. This is done by adding the line
#include <stdio.h>near the start of the program file.
If you do not do this, the compiler may start complaining about undefined functions or datatypes.
