scard

SCard refers to the Windows Smart Card API, a set of functions for interacting with smart cards and card readers. It is implemented in the Windows platform as part of the PC/SC standard and is exposed through the WinSCard library with headers such as WinSCard.h. Applications invoking these functions typically use the SCard prefix, for example SCardEstablishContext, SCardConnect, and SCardTransmit.

The PC/SC standard provides a cross-platform API for smart cards, and Windows implements it to enable communication with cards through readers via APDUs (Application Protocol Data Units). The SCard API abstracts hardware details and exposes common concepts such as contexts, readers, and card handles, enabling applications to work with different card types and readers in a uniform manner.

Key concepts and functions include: a context created with SCardEstablishContext, listing available readers with SCardListReaders, connecting to a card with SCardConnect, and transmitting commands with SCardTransmit. Protocols supported by cards include T=0, T=1, and sometimes RAW. Transaction safety can be ensured with SCardBeginTransaction and SCardEndTransaction. Additional attributes can be queried or set via SCardGetAttrib and SCardSetAttrib.

Typical workflow: establish a context, enumerate readers, connect to a card in a chosen reader, optionally begin a transaction, transmit APDUs and receive responses, end the transaction, disconnect from the card, and finally release the context.

Cross-platform use is common, as PC/SC is also implemented on macOS and Linux (via pcsc-lite), allowing portable smart card applications across major operating systems. See also PC/SC, WinSCard, and pcsc-lite.