A function in C can be called either with arguments or without arguments. These function may or may not return values to the calling functions. All C functions can be called either with arguments or without arguments in a C program.
When a function is called, we always supply one or more values to the function, called arguments.
return datatype function_name (list of arguments);
Arguments greatly increase the usefulness and flexibility of a function.
We also can call the function (void) without any arguments.
For Example :
int square (int a ); /* Here a is an argument of type int */
int square ( );
int square (void); /* These are the functions without any arguments */