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Streams are a portable way of reading and writing data. They provide a flexible and efficient means of I/O.

A Stream is a file or a physical device (e.g. printer or monitor) which is manipulated with a pointer to the stream.

There exists an internal C data structure, FILE, which represents all streams and is defined in stdio.h. We simply need to refer to the FILE structure in C programs when performing I/O with streams.

We just need to declare a variable or pointer of this type in our programs.

We do not need to know any more specifics about this definition.

We must open a stream before doing any I/O,

then access it

and then close it.

Stream I/O is BUFFERED: That is to say a fixed ``chunk'' is read from or written to a file via some temporary storage area (the buffer). This is illustrated in Fig. . NOTE the file pointer actually points to this buffer.

Fig. Stream I/O Model

This leads to efficient I/O but beware: data written to a buffer does not appear in a file (or device) until the buffer is flushed or written out. (n does this). Any abnormal exit of code can cause problems.
Wed Sep 14 10:06:31 BST 1994