The abbreviation TAPI stands for Telephony Application Programming Interface and refers to a programming interface for telephony applications. TAPI was originally developed by Microsoft and Intel and introduced as early as 1993. From Windows 95 onwards, the interface has been an integral part of the functionality and embedded in the software of that operating system. Since its introduction it has been updated several times and several different versions now exist. As of version 3.0, from 1999, the interface has also supported IP telephony and access video and audio streams, in addition to traditional telephone services. Part of the interface is the TAPI32.DLL, which provides standard functions for developing telephony applications. In turn, TAPI32.DLL communicates via the TSPI interface with the TAPI Service Provider, which translates the desired functions into a language that the hardware can interpret and then passes that on to the telephony hardware.

TAPI's functions

The main functions that TAPI can enable are the basics required for setting up calls, conducting conference calls and forwarding calls. In addition, typical office functions, such as database access, are made possible via Computer Telephony Integration (CTI). TAPI can be used for ISDN, analogue telephony, mobile telephony and voice over IP.

TAPI and Computer Telephony Integration

As part of the integration of telephony applications on computers, the TAPI can initiate calls from a PC, view data on incoming calls or indicate the status of extensions. In the Windows environment TAPI is the central component of Computer Telephony Integration, exchanging data with the telephone system. Communication with the telephone system is managed by the TAPI Service Provider (TSP). For example, email programs, such as Microsoft Outlook or IBM Notes, often use the TAPI to access software phone functions from within the software. One example of this is the function that allows stored contacts to be called directly with just a mouse click. Journal functions allow the person dealing with the call to directly enter contact data into a system during a call. This enables other users to immediately see the complete call history of a customer. This helps call centres to work much more efficiently.

Further information


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