C file input/output

The <a href="/facts/C_/Ky2No763">C programming language</a> provides many <a href="/facts/Standard_library/g9QS3vy0">standard library</a> <a href="/facts/Subroutine/9vFJrg0A">functions</a> for <a href="/facts/Computer_file/FjFH3Ufm">file</a> <a href="/facts/Input%2foutput/WQTE8Jas">input and output</a>. These functions make up the bulk of the <a href="/facts/C_standard_library/qdG1nW2c">C standard library</a> <a href="/facts/Header_file/fg3KEG4V">header</a> <stdio.h>. The functionality descends from a "portable I/O package" written by <a href="/facts/Mike_Lesk/zkpvNVh0">Mike Lesk</a> at <a href="/facts/Bell_Labs/fKP5Gk0H">Bell Labs</a> in the early 1970s, and officially became part of the <a href="/facts/Unix/0pNL2seI">Unix</a> operating system in <a href="/facts/Version_7_Unix/ju5nRs7k">Version 7</a>.
The I/O functionality of C is fairly low-level by modern standards; C abstracts all file operations into operations on <a href="/facts/Stream_(computing)/2jtBAp0U">streams</a> of <a href="/facts/Byte/BNHUp9Qq">bytes</a>, which may be "input streams" or "output streams". Unlike some earlier programming languages, C has no direct support for <a href="/facts/Random_access/1cxrCk3r">random-access</a> data files; to read from a record in the middle of a file, the programmer must create a stream, <a href="/facts/Fseek/m5n82Fqz">seek</a> to the middle of the file, and then read bytes in sequence from the stream.
The stream model of file I/O was popularized by Unix, which was developed concurrently with the C programming language itself. The vast majority of modern operating systems have inherited streams from Unix, and many languages in the C programming language family have inherited C's file I/O interface with few if any changes (for example, <a href="/facts/PHP/vU6YRJX0">PHP</a>).

C file input/output open-in-new

C file input/output