A mainframe is
|“||[a]n industry term for a large computer, typically used for the commercial applications of businesses and other large-scale computing purposes. Generally, a mainframe is associated with centralized rather than distributed computing.||”|
|“||[a] large computer that [is] capable of supporting thousands of simultaneous users. Although historically they have been associated with centralized computing, today's mainframes can be used in networks to serve distributed users and smaller servers.||”|
- FFIEC IT Examination Handbook, Operations, Appendix B: Glossary (full-text).
- Technology Assessment: Cybersecurity for Critical Infrastructure Protection, at 141.