Big Red Switch

From Wikipedia, the free encyclopedia

An IBM System/360 Model 65 operator's console, with "Big Red Switch" (upper right).
An IBM System/360 Model 65 operator's console, with "Big Red Switch" (upper right).

Big Red Switch (BRS) is a hacker term for the shutdown button or power switch on a computer, especially the red "Emergency Pull" switch on IBM mainframe operator consoles. The term has also sometimes been used for the power switch on IBM PCs.

On some mainframe designs the emergency power off switch would immediately physically disable the machine's power supply. Because the use of a Big Red Switch would bring down a computer in an "uncontrolled fashion", getting the machine up and running again could be a nontrivial and cumbersome task taking quite some time. Therefore, particularly in the early mainframe computer era, people risked disciplinary action for pulling/pushing the BRS of a production batch processing mainframe if this action was not absolutely necessary as part of an emergency (see molly-guard).

This article was originally based on material from the Free On-line Dictionary of Computing, which is licensed under the GFDL.

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