C Primer Plus, Fourth Edition

Behind the Scenes with Standard I/O

Now that you've seen some of the features of the standard I/O package, let's examine a representative conceptual model to see how standard I/O works.

Normally, the first step in using standard I/O is to use fopen() to open a file. (Recall, however, that the stdin, stdout, and stderr files are opened automatically.) The fopen() function not only opens a file but sets up a buffer (two buffers for read-write modes), and it sets up a data structure containing data about the file and about the buffer. Also, fopen() returns a pointer to this structure so that other functions know where to find it. Assume that this value is assigned to a pointer variable named fp. The fopen() function is said to open a stream. If ...