a. Write a program, that asks the user to input a digit between 0 and 9.

b. Test the input from the user and display an error message if the returned value is not a digit. The program should then be terminated. If the test is successful, the program should print the input value on the computer screen.

Exercise 4.3 You can use the getchar () function in C to get character input from the user through the keyboard. This function stops the execution of the program and waits for the input from the user