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The C programming language provides many standard library functions for file input and output.These functions make up the bulk of the C standard library header <stdio.h>. [1] The functionality descends from a "portable I/O package" written by Mike Lesk at Bell Labs in the early 1970s, [2] and officially became part of the Unix operating system in Version 7.
printf(string format, items-to-format) It can take one or more arguments, where the first argument is a string to be written. This string can contain special formatting codes which are replaced by items from the remainder of the arguments. For example, an integer can be printed using the "%d" formatting code, e.g.: printf("%d", 42);
More generally, Python 2.x specifies the built-in file objects as being “implemented using C's stdio package," [48] and frequent reference is made to C standard library behaviors; the available operations (open, read, write, etc.) are expected to have the same behavior as the corresponding C functions (fopen, fread, fwrite, etc.).
C source files contain declarations and function definitions. Function definitions, in turn, contain declarations and statements. Declarations either define new types using keywords such as struct, union, and enum, or assign types to and perhaps reserve storage for new variables, usually by writing the type followed by the variable name.
C functions are akin to the subroutines of Fortran or the procedures of Pascal. A definition is a special type of declaration. A variable definition sets aside storage and possibly initializes it, a function definition provides its body. An implementation of C providing all of the standard library functions is called a hosted implementation.
On POSIX systems, the file descriptor for standard input is 0 (zero); the POSIX <unistd.h> definition is STDIN_FILENO; the corresponding C <stdio.h> abstraction is provided via the FILE* stdin global variable. Similarly, the global C++ std::cin variable of type <iostream> provides an abstraction via C++ streams.
The C POSIX library is a specification of a C standard library for POSIX systems. It was developed at the same time as the ANSI C standard. Some effort was made to make POSIX compatible with standard C ; POSIX includes additional functions to those introduced in standard C.
The format string used in strftime traces back to at least PWB/UNIX 1.0, released in 1977. Its date system command includes various formatting options. [2] [3] In 1989, the ANSI C standard is released including strftime and other date and time functions. [4]