A large program is subdivided into a number of smaller programs or subprograms. Each
subprogram specifies one or more actions to be performed for a large program. such

subprograms are functions.

The function supports only static and extern storage classes. By default, function assumes

extern storage class. functions have global scope. Only register or auto storage class is

allowed in the function parameters. Built-in functions that predefined and supplied along with

the compiler are known as built-in functions. They are also known as library functions.