This example will not validate, process or store a credit card. It will however, verify a credit card number based on some standardized criteria. Distinct credit card types have unique prefixes (usually the 1st 4 numbers) set by the credit card companies themselves and a specific digit length for the account number. This function will check that as well as test the expiration date against today's date. This function returns True if credit card info appears to be valid or False if the information does not pass the standardized criteria established for specific credit cards.