Credit Card Numbers - Visa. These Credit card numbers validate for Visa credit cards. The number and information is as real as it can be, and contains valid bin information. The structure of the credit card number starts with a valid bin number and also validates against the LUHN's formula.
UART is a protocol (Universal asynchronous receiver/transmitter ) for serial transfer of information. You ask about an embedded system with mentioning which so I'll assume that you have a block diagram with one indicating UART.
UAC is a security feature of Windows Vista, Windows 7 and Windows 8 which helps prevent unauthorized changes to your computer. These changes can be initiated by applications, viruses or other users. User Account Control makes sure these changes are made only with approval from the administrator. If the changes are not approved by the administrator, they are not executed and Windows remains unchanged. It is as if nothing happened.