What might be the origin of the word "mainframe" for describing a type of computer?

  • 2
    Voting to close as a general reference question that could be found easily in a quick web search.
    – Robusto
    Commented Jun 2, 2011 at 18:41
  • 10
    Web search does not turn up a specific first use or earliest reference.
    – hotpaw2
    Commented Jun 2, 2011 at 19:01

4 Answers 4


The word is formed (obviously) from the adjective main applied to frame, which tends to coalesce into mainframe in any context where a particular main frame becomes a standard component and needs a noun for convenient reference. For example, the term was used for the main frames of locomotives and early automobiles. A particularly relevant such use is in telephone infrastructure, where there was a large frame used for an exchange, holding wiring and relays for a group of phone lines with a common prefix. For instance, in this 1918 article, the diagram has an arrow labeled "to new exchange mainframe".

Early computers used a large frame (much larger than "racks" used now) to hold wiring and components for part of a computer (like that shown here). By the late 1950s, a typical installation might have a single large frame holding the central processing unit, to which bundles of wires from peripherals ran. To those familiar with the similar usage in telephone technology, mainframe would have been a natural usage for this CPU frame. For example, in this 1961 article, a Western Electric (of AT&T) staff member writes:

Likewise, the output of a computer mainframe is digital...

The term became more widely adopted, in particular for the large central computer used by a company as distinguished from smaller computers which began to appear in the 1960s. It is not terribly surprising that the earliest source quoted by the Oxford English Dictionary for mainframe is a 1964 glossary from Honeywell, then a producer (among other things) of smaller computers and soon minicomputers.

  • 3
    So "mainframe" may have been common preexisting engineering terminology for a big rack of central telephone exchange equipment, reapplied to the new big digital equipment filling the same type of floor space?
    – hotpaw2
    Commented Jun 2, 2011 at 20:45
  • 2
    hotpaw2: Essentialy, yes. A large rack of wiring and components in both cases. The technologies were related too; some of the earliest computers used relays (like telephone exchanges) rather than vacuum tubes or transistors.
    – mgkrebbs
    Commented Jun 2, 2011 at 20:58

Actually, IBM did use the term right from the beginning. Gene Amdahl (one of the lead designers of the System/360 mainframe) used the term in 1964 in an IBM journal describing the S/360 architecture.

  • see G.M. Amdahl, G.A. Blaauw, and F.P. Brooks, Jr., "Architecture of the IBM System/360," IBM JOURNAL OF RESEARCH AND DEVELOPMENT, 8, no. 2 (1964)

Etymonline gives this:

"central processor of a computer system," 1964, from main (adj.) + frame.

In the days when large installations were becoming more common, a computer system would require a specially built room (as far as I know, they still do). Tape drives, disk drives, printers, card readers and the like would be distributed about the space. The "mainframe" refers in such cases to the processing unit and physical memory - which in the case of an IBM 360-158 was about the size of a commercial refrigerator.

  • According to Wikipedia, "The term originally referred to the large cabinets that housed the central processing unit and main memory of early computers." So it was really more about the cabinet and supporting "frame" to which the memory and CPU were bolted.
    – Robusto
    Commented Jun 2, 2011 at 18:50
  • Which early computer?
    – hotpaw2
    Commented Jun 2, 2011 at 19:00
  • Yes Robusto. The CPU and memory were housed in a large frame, "about the size of a commercial refrigerator." But when operators referred to "the mainframe," we were not talking about the housing of the unit per se.
    – The Raven
    Commented Jun 2, 2011 at 19:05
  • Was (adj.)+frame ever used as a term for stuff other than the main CPU and memory mounted in frames or racks? Also, some early minicomputers were also mounted in frames or racks, but not called mainframes.
    – hotpaw2
    Commented Jun 2, 2011 at 19:06
  • 2
    @hotpaw2 Yes, for instance, the IBM 360/50 had a Storage Frame, Power Frame, and CPU Frame. The frame was the standardized refrigerator-sized box that IBM used to hold components. See bitsavers.org/pdf/ibm/360/fe/2050/SY22-2832-4_360-50Maint.pdf The interesting issue is the transition of "mainframe" from describing a part of the computer to describing a type of computer. Commented Sep 3, 2019 at 21:16

Frame in the mechanical sense of board - although in the early machines it would be a framework of wired connections rather a than a printed circuit board.

The main frame was the central piece containing the processing unit, with other auxiliary frames containing memory, I/O, peripherals etc.

The first mainframe in modern terms was probably the IBM360 in the mid 1960's but IBM never used the term - in fact IBM pretty much avoided the term computer at the time.

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