Using the lineGetCallStatus function, an application can receive complete call status information for the specified call as a data structure of type LINECALLSTATUS. The lineGetCallInfo function returns mostly constant information about a call as a data structure of the type LINECALLINFO. The message LINE_CALLSTATE is sent unsolicited to an application to notify it about changes in a call's state.
The call-information data structure maintained for each call contains an application-specific member that applications can read from and write to. This member is not interpreted by TAPI. Applications can use it to tag calls in application-specific ways. Writing to this member so that the change is visible to other applications can be done with the lineSetAppSpecific function.