Westi (Westinghouse Teleprocessing Interface System) was one of two early local teleprocessing packages for IBM's DOS/VSE environment. Westi stood for Westinghouse Terminal Interactive. Westi provided an interface and access method for programmers to 'talk' to monitors and handle data entry. Such access methods later became known as APIs and the handlers a form of transaction processing. In 1981, WESTI was considered the main competitor to CICS, holding second place in market share for IBM mainframe transaction processing monitors.