Final answer:
To extend a program to accept a dash (-) as an input for no service, you would modify the input validation section to recognize a dash as a valid input. This could be implemented by checking if the entered character is a dash, and if so, processing it accordingly by setting an appropriate variable to represent the absence of service.
Step-by-step explanation:
To extend a program to allow the user to enter a dash (-) to indicate no service, you will need to modify the input validation part of the code to accept a dash as a permissible character or input option. For example, if the program is written in Python, you could use an if statement to check if the user has entered a dash: user_ input = input('Enter service code or dash (-) for no service: '), if user_ input == '-': print('No service selected.'), else: # Proceed with the normal processing of service code.
In this code snippet, the program prompts the user for a service code. If the user enters a dash, the program acknowledges that no service has been selected. Otherwise, the program continues with normal processing. You need to ensure that the rest of your code can handle the dash input appropriately, potentially by setting a variable to None or a similar value that represents an absence of service.