Pointer Variables

	Chapter 11 - Complete I/O in C
	Visual C++ 6: The Complete Reference
	Chris H. Pappas and William H. Murray, III

Copyright 1998 The McGraw-Hill Companies

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	Low-level Input and Output in C

	Table 11-1 lists the most commonly used low-level input and output functions used by an application.

	Table 11-1: Commonly Used Low-level Input and Output Functions

	Function

Definition

	close( )

Closes a disk file

	lseek( )

Seeks to the specified byte in a file

	open( )

Opens a disk file

	read( )

Reads a buffer of data

	unlink( )

Removes a file from the directory

	write( )

Writes a buffer of data

	Low-level input and output calls do not buffer or format data. Files opened by low-level calls are referenced by a file handle (an integer value used by the operating system to refer to the file). You use the open( ) function to open files. You can use the sopen( ) macro to open a file with file-sharing attributes.

	Low-level functions are different from their stream counterparts because they do not require the inclusion of the STDIO.H header file. However, some common constants that are predefined in STDIO.H, such as EOF and NULL, may be useful. Declarations for the low-level functions are given in the IO.H header file.

	This second disk-file I/O system was originally created under the UNIX operating system. Because the ANSI C standard committee has elected not to standardize this low-level, UNIX-like, unbuffered I/O system, it cannot be recommended for future use. Instead, the standardized buffered I/O system described throughout this chapter is recommended for all new projects.

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