CAPI

CAPI is an acronym used in multiple domains, most often in computing and telecommunications. It does not refer to one universal standard, but to several distinct interfaces or standards that share the same letters. The precise meaning depends on the context in which it is used.

In software development, a C API, short for a C application programming interface, describes a set of functions, types, and conventions exposed by a library or service. A C API defines how other programs can call into the library, what data structures to use, and how errors are reported. C APIs are fundamental for enabling interoperability between languages and for building modular software that can be extended with plug-ins or bindings to languages beyond C.

Common ISDN Application Programming Interface, abbreviated CAPI, is a specific telecommunications standard for ISDN hardware. It provides a standardized set of functions for tasks such as dialing, answering, and managing calls, as well as accessing device status and events. CAPI originated to simplify software development for PC-based ISDN telephony and remains a reference in some regional implementations and legacy systems.

CryptoAPI, often shortened to CAPI, refers to Windows CryptoAPI, a set of cryptographic functions that provide services like encryption, decryption, digital signatures, and certificate management. It has been complemented and gradually superseded by newer APIs in modern Windows environments, but remains a notable meaning of the acronym in security contexts.

Other uses of the acronym exist in different industries and projects. Because CAPI can denote multiple concepts, the intended meaning is typically inferred from the surrounding domain and accompanying explanation.