Search results
Results from the WOW.Com Content Network
An example of the printf function. printf is a C standard library function that formats text and writes it to standard output. The name, printf is short for print formatted where print refers to output to a printer although the functions are not limited to printer output. The standard library provides many other similar functions that form a ...
For example, an integer can be printed using the "%d" formatting code, e.g.: printf("%d", 42); This formats the integer "42" as text and prints it to the standard output. printf is typically the first function any C programmer encounters, because it is the only function which appears in the standard Hello world program:
In the above example, the main( ) function defines where the program should start executing. The function body consists of a single statement , a call to the printf() function, which stands for " print f ormatted"; it outputs to the console whatever is passed to it as the parameter , in this case the string "hello, world" .
It provides facilities for stepping through a list of function arguments of unknown number and type. C++ provides this functionality in the header cstdarg. The contents of stdarg.h are typically used in variadic functions, though they may be used in other functions (for example, vprintf) called by variadic functions.
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.
Some compilers (for example, GCC [7]) provide built-in versions of many of the functions in the C standard library; that is, the implementations of the functions are written into the compiled object file, and the program calls the built-in versions instead of the functions in the C library shared object file.
In C and C++, the type signature is declared by what is commonly known as a function prototype. In C/C++, a function declaration reflects its use; for example, a function pointer with the signature (int)(char, double) would be called as:
Variadic macros are particularly useful when writing wrappers to functions taking a variable number of parameters, such as printf, for example when logging warnings and errors. One little-known usage pattern of the C preprocessor is known as X-Macros. [6] [7] [8] An X-Macro is a header file.