Write a computer program that will ask the user to input a three- or four-digit code for aluminum alloys. You will have to ask the user to provide one digit at a time or figure out a way of comparing...

Write a computer program that will ask the user to input a three- or four-digit code for aluminum alloys. You will have to ask the user to provide one digit at a time or figure out a way of comparing different digits in a string. This will be followed by a letter and a number.