• Library functions in C language are inbuilt functions which are grouped together and placed in a common place called library.
• Each library function in C performs specific operation.
• We can make use of these library functions to get the pre-defined output instead of writing our own code to get those outputs.
• These library functions are created by the persons who designed and created C compilers.
• All C standard library functions are declared in many header files which are saved as filename.h
• We are including these header files in our C program using “#includes<filename.h>” command to make use of the functions those are declared in the header files.
• When we include header files in our C program using “#include<filename.h>” command, all C code of the header files are included in C program. Then, this C program is compiled by compiler and executed.
List of most used header files in C :
Check the below table to know all the C library functions and header files in which they are declared.