Bomb (symbol)

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A Mac OS bomb screen.
A Mac OS bomb screen.

The Bomb icon is a symbol designed by Susan Kare that was displayed when a "classic" Macintosh operating system (pre-Mac OS X) program had an application crash. It was similar to a dialog box in Windows 9x that said "This program has performed an illegal operation and will be shut down". But, since the "classic" Mac OS offered no memory protection, a system crash would take down the entire system, unlike Mac OS X and Windows NT which only force-quit the offending program.

The bomb symbol first appeared on the original Macintosh in 1984. Often, a reason for the crash including the error code was displayed in the dialog. If a person was lucky, a "Continue" button would be an option, which could be used to dismiss the dialog and force the offending program to quit, but most often the computer would have to be restarted. The debugger program MacsBug was sometimes used even by end users to provide basic (though not always reliable) error recovery, and could be used for troubleshooting purposes much as the output of a Unix kernel panic or a Windows NT Blue Screen of Death could be. MacOS Classic bomb boxes were often ridiculed for providing little or no useful information about the error; this was a conscious decision by the Macintosh team to eliminate any information that the end user could not make sense of.

In Mac OS X, the bomb symbol is no longer used since the system architecture is vastly different from that in the classic Mac OS, and an application crash rarely brings down the entire system. A kernel panic screen (either text overwritten on the screen in older versions, or simplified to a reboot message in more recent versions) replaces the bomb symbol but appears less often due to the radically different process management model.

TOS-based systems, such as the Atari ST, also used bombs as the indication for an error. When a system error occurred, a row of bombs, variable in number, would show up on the screen and then disappear. A complete system crash resulted in the screen filled with bombs, which could not be removed without a hard reboot.

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