Thanks Ada J.

Actually, I want to develop a door access control system with smartcards in a college. Several smartcard readers will be connected to a single PC through the serial ports. The smartcard ID and the time will be logged when an entry is made and so a real time clock, which is controlled by the same PC as the smartcard readers, will be placed next to the readers.

Depending on the complexity, alphabetic LCD or LED array will be chosen.

But I have no idea how to manage all these things together.

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Winson