Files Versus Streams
The C language provides a set of rich library functions to perform input and output (I/O) operation. Those functions can read or write any type of data to files. Before we go any further in discussing the C I/O functions, let's first understand the definitions of files and streams in C.
What Is a File?
In C, a file can refer to a disk file, a terminal, a printer, or a tape drive. In other words, a file represents a concrete device with which you want to exchange information. Before you perform any communication to a file, you have to open the file. Then you need to close the opened file after you finish exchanging information with it.
What Is a Stream?
The data flow you transfer from your program to a file, or vice versa, is called a stream, which is a series of bytes. Not like a file, a stream is device-independent. All streams have the same behavior. To perform I/O operations, you can read from or write to any type of files by simply associating a stream to the file.
There are two formats of streams. The first one is called the text stream, which consists of a sequence of characters (that is, ASCII data). Depending on the compilers, each character line in a text stream may be terminated by a newline character. Text streams are used for textual data, which has a consistent appearance from one environment to another, or from one machine to another.
The second format of streams is called the binary stream, which is a series of bytes. The content of an .exe file would be one example. Binary streams are primarily used for nontextual data, which is required to keep the exact contents of the file.
Buffered I/O
In C, a memory area, which is temporarily used to store data before it is sent to its destination, is called a buffer. With the help of buffers, the operating system can improve efficiency by reducing the number of accesses to I/O devices (that is, files).
By default, all I/O streams are buffered. The buffered I/O is also called the high-level I/O. Accordingly, the low-level I/O refers to the unbuffered I/O.
