Different type of function
There are two kind of function:
1. User defined function
2. Library function
User defined function:
User defined function is small or sub function created by programmer.
Library function is some reserved function in c compiler such as printf();, scanf(); etc. If you write printf(); the reserved commands for printf() function inside stdio.h file will be executed.
Look at this program
printf("function1 is called to main function n");
function1(); //function is calling
Analysis: In the program ‘function1’ is a user defined function and ‘printf()’ is a library function.