TPF evolved from the Airlines Control Program (ACP), a free package developed in the mid-1960s by IBM in association with major North American and European Airlines. In 1979, TPF was introduced by IBM to substitute ACP, as a priced software product.
TPF is designed for fast, high-volume, high-throughput transaction processing, handling large continuous loads of essentially simple transactions across large, geographically dispersed, networks. The world's largest TPF-based systems, running on multiple IBM mainframes, are capable of processing tens of thousands of transactions per second.
TPF is also designed for highly reliable continuous (24 x 7 x 365) operation.
TPF implements an API known as the PARS API, on which many Airline and Financial systems are based.
(More details?). See also ALCS.