IBM began operations in 1911 as the Computing-Tabulating-Recording Co. (CTR). In 1914, under the direction of Thomas J. Watson, CTR became IBM (International Business Machines). In 1953, IBM announced its first computer, the model 701, and shortly after, the model 650, which became its most popular model during the 1950s. The standard-setting computer for all modern IBM systems, the System/360, was introduced in 1964. An alternative line of computers, starting with the System/3, was introduced in 1970. The AS/400 is the current model in this series.

Mainframes are not going away any time soon. They still house up to 70 percent of the world data. This legacy data and the systems that store it will no doubt keep old IBM engineers and programmers busy with consulting work for years. In fact, IBM mainframes have been reborn in much smaller server-size packages that run older software and provide connections to legacy data.

Starting in the mid-1990s, many IBM sites using SNA systems and APPN began moving to TCP/IP rather than using IBM networking schemes. In fact, IBM and other vendors like Cisco are developing hardware and software for integrating legacy systems into TCP/IP networks, not the other way around. These are discussed under "IBM Host Connectivity."