Programming Exercise (25 points): (Call the Source code Exercisel.c) Write a routine/function that takes as input a character c supposed to be a binary digit and returns an integer representing the value of the digit c. If c is not a binary digit, your function must return -1. Use this function to implement a program that prompts the user to enter a character c that represents a binary digit (a bit) (Recall that c can be only '0' or'l). Your program must use the character type for the input. If the user enters a character x' that is NOT a binary digit, you must print out the error message: "The characterx is invalid: x is not a bit"If the character c is a bit, your man program must return an integer representing the value of the digit and print out that value in decimal. Example I: If the user enters the character '0, your program must print out the value 0. Example 2: If the user enters the character, your program must print out the value Example 4: If the user enters the character 'B', your program must print out the error message: The character B is invalid: B is not a bit