<messaging> (MAPI) A messaging architecture and a client interface component for applications such as {electronic mail}, scheduling, calendaring and document management. As a messaging architecture, MAPI provides a consistent interface for multiple application programs to interact with multiple messaging systems across a variety of hardware platforms. MAPI provides better performance and control than {Simple MAPI}, Common Messaging Calls (CMC) or the {Active Messaging Library}. It has a comprehensive, open, dual-purpose interface, integrated with Microsoft Windows. MAPI can be used by all levels and types of client application and "service providers" - driver-like components that provide a MAPI interface to a specific messaging system. For example, a word processor can send documents and a workgroup application can share and store different types of data using MAPI. MAPI separates the programming interfaces used by the client applications and the service providers. Every component works with a common, Microsoft Windows-based user interface. For example, a single messaging client application can be used to receive messages from fax, a bulletin board system, a host-based messaging system and a LAN-based system. Messages from all of these systems can be delivered to a single "universal Inbox". MAPI is aimed at the powerful, new market of workgroup applications that communicate with such different messaging systems as fax, DEC All-In-1, voice mail and public communications services such as AT&T Easylink Services, CompuServe and MCI MAIL. Because workgroup applications demand more of their messaging systems, MAPI offers much more than basic messaging in the programming interface and supports more than local area network (LAN)-based messaging systems. Applications can, for example, format text for a single message with a variety of fonts and present to their users a customised view of messages that have been filtered, sorted or preprocessed. MAPI is built into Windows 95 and Windows NT and can be used by 16-bit and 32-bit Windows applications. The programming interface and subsystem contained in the MAPI DLL provide objects which conform to the {Component Object Model}. MAPI includes standard messaging client applications that demonstrate different levels of messaging support. MAPI provides cross platform support through such industry standards as SMTP, X.400 and Common Messaging Calls. MAPI is the messaging component of {Windows Open Services Architecture} (WOSA). [Correct expansion? Relatonship with Microsoft?] (1997-12-03)

<programming> (API, or "application programming interface") The interface (calling conventions) by which an {application program} accesses operating system and other services. An API is defined at source code level and provides a level of abstraction between the application and the kernel (or other privileged utilities) to ensure the portability of the code. An API can also provide an interface between a {high level language} and lower level utilities and services which were written without consideration for the calling conventions supported by compiled languages. In this case, the API's main task may be the translation of parameter lists from one format to another and the interpretation of call-by-value and call-by-reference arguments in one or both directions. (1995-02-15)

Application Programming Interface