TAPI 3.0 (TAPI/COM) or TAPI 2.2 (TAPI/C)?

Microsoft's COM-based telephony API, currently version TAPI 3.0, is new with Windows 2000. TAPI/COM provides greatly enhanced development tools for the modern world of communication programming, where a "call" may be a video stream on an IP-based network and an actual phone set isn't involved at any point in the session. Generally speaking, application writers will find TAPI/COM gives them more capacity to implement flexible communications controls.

However, TAPI/C may be the right choice in some situations. If minor modifications are needed for a legacy application, conversion to the COM API may not be cost effective.