A function is a block of code that performs some operation.

The user-defined functions are further divided into four types on the basis of arguments and return value processing:

• Functions with arguments and return values.
• Functions with arguments and without return values.
• Functions without arguments and with return values.
• Functions without arguments and without return values.

A function is a block of code that performs some operation. A function can optionally define input parameters that enable callers to pass arguments into the function. A function can optionally return a value as output