Library (Built-in) Vs User Defined Function (Difference)

C functions are broadly classified into two major categories, namely, library or built – in functions and user defined functions.

This article addresses major differences between library or built – in function and user defined function in C programming.

Difference between Library and User Defined Function

Functions which are already defined, compiled and stored in different header file of C Library are known as Library Functions.

Those functions which are definby programmers according to their need are known as User Defined Functions.


These functions cannot be modified by user.

These functions can be modified by user.


Users do not know the internal working of these type of functions.

Users understand the internal working of these type of functions.


For Example: printf(), scanf(), getch(), clrscr(), pow() etc.

For Example: 


void message()
{
    printf(“Welcome to C.”);
}
Here message() is user defined function.