Prompt the user to enter a string that represents a four character binary

number

$$ Validate user input by applying two criteria:

$$ If the user input is not four characters in length, inform the user that the input

is not valid; terminate the program

$$ If any character is not a zero or $1,$ inform the user that this is not a valid binary

number; terminate the program.

$$ If the user$$s input is a valid four digit binary number, convert to the

equivalent base ten representation

$3$