Prerequisite – C language
C standard library (libc) is the standard library for the C programming language, as specified in the ANSI C standard. C standard library is also called the ISO C library.
The C library functions are provided by the system and stored in the library. The C library function is also called an in-built function in C programming. To use Inbuilt Function in C, you must include their respective header files, which contain prototypes and data definitions of the function.
For example, printf() is a library function used to print on the console and defined in stdio.h (full form : Standard Input/Output) C library. stdio.h has following functionalities in C.
- printf() is output to the screen
- scanf() is read input from the screen
- getchar() is return characters typed on screen
- putchar() is output a single character to the screen
- fopen() is open a file, and
- fclose() is close a file
These are various C standard library :
| Full Form | Header File | Functions |
|---|---|---|
| Standard input-output header | <stdio.h> | Used to perform input and output operations like scanf() and printf(). |
| Console input-output header | <conio.h> | Used to perform console input and console output operations like clrscr() to clear the screen and getch() to get the character from the keyboard. |
| String header | <string.h> | Used to perform string manipulation operations like strlen and strcpy. |
| Standard library header | <stdlib.h> | Used to perform standard utility functions like dynamic memory allocation using functions such as malloc() and calloc(). |
| Math header | <math.h> | Used to perform mathematical operations like sqrt() and pow() to obtain the square root and the power of a number respectively. |
| Time header | <time.h> | Used to perform functions related to date and time like setdate() and getdate() to modify the system date and get the CPU time respectively. |
| Character type header | <ctype.h> | Used to perform character type functions like isaplha() and isdigit() to find whether the given character is an alphabet or a digit. respectively. |
| Assertion header | <assert.h> | Used in program assertion functions like assert() to get an integer data type as a parameter which prints stderr only if the parameter passed is 0. |
| Localization header | <locale.h> | Used to perform localization functions like setlocale() and localeconv() to set locale and get locale conventions respectively. |
| Signal header | <signal.h> | Used to perform signal handling functions like signal() and raise() to install signal handler and to raise the signal in the program respectively. |
| Jump header | <setjmp.h> | Used to perform jump functions. |
| Standard argument header | <stdarg.h> | Used to perform standard argument functions like va_start and va_arg() to indicate the start of the variable-length argument list and to fetch the arguments from the variable-length argument list in the program respectively. |
| Error handling header | <errno.h> | Used to perform error handling operations like errno() to indicate errors in the program by initially assigning the value of this function to 0 and then later changing it to indicate errors. |
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