Mainframe computer

A pair of IBM mainframes. On the left is the IBM z Systems z13. On the right is the IBM LinuxONE Rockhopper.
An IBM System z9 mainframe

Mainframe computers or mainframes (colloquially referred to as "big iron")[1] are computers used primarily by large organizations for critical applications; bulk data processing, such as census, industry and consumer statistics, enterprise resource planning; and transaction processing. They are larger and have more processing power than some other classes of computers: minicomputers, servers, workstations, and personal computers.

The term originally referred to the large cabinets called "main frames" that housed the central processing unit and main memory of early computers.[2][3] Later, the term was used to distinguish high-end commercial machines from less powerful units.[4] Most large-scale computer system architectures were established in the 1960s, but continue to evolve. Mainframe computers are often used as servers.


Modern mainframe design is characterized less by raw computational speed and more by:

  • Redundant internal engineering resulting in high reliability and security
  • Extensive input-output ("I/O") facilities with the ability to offload to separate engines
  • Strict backward compatibility with older software
  • High hardware and computational utilization rates through virtualization to support massive throughput.
  • Hot-swapping of hardware, such as processors and memory.

Their high stability and reliability enable these machines to run uninterrupted for very long periods of time, with mean time between failures (MTBF) measured in decades.

Mainframes have high availability, one of the primary reasons for their longevity, since they are typically used in applications where downtime would be costly or catastrophic. The term reliability, availability and serviceability (RAS) is a defining characteristic of mainframe computers. Proper planning and implementation is required to realize these features. In addition, mainframes are more secure than other computer types: the NIST vulnerabilities database, US-CERT, rates traditional mainframes such as IBM Z (previously called z Systems, System z and zSeries), Unisys Dorado and Unisys Libra as among the most secure with vulnerabilities in the low single digits as compared with thousands for Windows, UNIX, and Linux.[5] Software upgrades usually require setting up the operating system or portions thereof, and are non-disruptive only when using virtualizing facilities such as IBM z/OS and Parallel Sysplex, or Unisys XPCL, which support workload sharing so that one system can take over another's application while it is being refreshed.

In the late 1950s, mainframes had only a rudimentary interactive interface (the console), and used sets of punched cards, paper tape, or magnetic tape to transfer data and programs. They operated in batch mode to support back office functions such as payroll and customer billing, most of which were based on repeated tape-based sorting and merging operations followed by line printing to preprinted continuous stationery. When interactive user terminals were introduced, they were used almost exclusively for applications (e.g. airline booking) rather than program development. Typewriter and Teletype devices were common control consoles for system operators through the early 1970s, although ultimately supplanted by keyboard/display devices.

By the early 1970s, many mainframes acquired interactive user terminals[NB 1] operating as timesharing computers, supporting hundreds of users simultaneously along with batch processing. Users gained access through keyboard/typewriter terminals and specialized text terminal CRT displays with integral keyboards, or later from personal computers equipped with terminal emulation software. By the 1980s, many mainframes supported graphic display terminals, and terminal emulation, but not graphical user interfaces. This form of end-user computing became obsolete in the 1990s due to the advent of personal computers provided with GUIs. After 2000, modern mainframes partially or entirely phased out classic "green screen" and color display terminal access for end-users in favour of Web-style user interfaces.[citation needed]

The infrastructure requirements were drastically reduced during the mid-1990s, when CMOS mainframe designs replaced the older bipolar technology. IBM claimed that its newer mainframes reduced data center energy costs for power and cooling, and reduced physical space requirements compared to server farms.[6]

Other Languages
العربية: حاسوب كبير
azərbaycanca: Meynfreym
čeština: Mainframe
dansk: Mainframe
Deutsch: Großrechner
eesti: Suurarvuti
español: Unidad central
한국어: 메인프레임
Bahasa Indonesia: Komputer bingkai utama
italiano: Mainframe
latviešu: Lieldators
македонски: Мејнфрејм сметач
монгол: Мэйнфрэйм
Nederlands: Mainframe
norsk: Stormaskin
polski: Mainframe
português: Mainframe
română: Mainframe
русский: Мейнфрейм
Simple English: Mainframe computer
slovenčina: Mainframe
slovenščina: Osrednji računalnik
српски / srpski: Мејнфрејм рачунар
srpskohrvatski / српскохрватски: Mejnfrejm računar
svenska: Stordator
Türkçe: Anabilgisayar
українська: Мейнфрейм
Tiếng Việt: Máy tính lớn
ייִדיש: מיינפריים