Accessing a Function

 A function can be accessed (i.e. called) by specifying its name, followed by a list of arguments enclosed in parenthesis and separated by commas. If the function call does not require any arguments, an empty pair of parenthesis must follow the name of the function. The argument appearing in the function call is referred to as actual arguments, in contrast to the formal arguments that appear in the first line of the function definition.  If the function returns a value, the function access is often written as an assignment statement; e.g.

y=polynomial (x);

This function access causes the value returned by the function to be assigned to the variable y. On the other hand, if the function does not return anything, the function access appears by itself; e.g.

display (a, b, c);

This function access causes the values of a, b and c to be processed internally (i.e. displayed) within the function.

C program has two types of functions

(a)    Library function

(b)   User defined function