Blue screen of death
The so-called Blue Screen of Death, also written as BSoD for short, refers to the screen displayed by Microsoft's Windows operating system when it cannot (or is in danger of being unable to) recover from a system error.
The Windows NT operating system's kernel generally cannot recover from the error, and the only action a user can take is to restart the operating system, losing all unsaved work and possibly breaking the consistency of the file system. The information displayed on the Blue Screen of Death is often not enough to determine what went wrong, even for someone with access to the source code (for example, it does not contain a stack dump, and if it did, it would be a lot of work to copy it somewhere else since you cannot save the data displayed at the screen at this point). It only displays what point the code crashed at, which can be completely different from where the error originated, and thus can mislead users into believing it is a hardware error or similar.
Microsoft's desktop operating systems Windows 95, 98, and ME also at times indicate problems with a display of somewhat cryptic information on what has also come to be called the Blue Screen of Death. However, these screens give the user some options, some with a hope of continuing, and thus this is also referred to simply, and perhaps more properly, as just a "blue screen"--the "death" of the operating system is not always imminent. The most common reason for BSoD'ing is problems with incompatibe versions of DLLs. Windows loads these into memory when they are needed by application programs; if versions are changed, the next time an application loads the DLL it may be different from what the application expects. These incompatibilities increase over time as more new software is installed, and is one of the main reasons why a freshly-installed copy of Windows is more stable than an "old" one.
By default, the display is white (CGA color 0x0F; HTML color #FFFFFF) lettering on a blue
(EGA color 0x01; HTML color #0000AA) background, with information about current memory values
and register values.
Showing they have a sense of humor, Microsoft has added a utility that allows the user to change a setting
in system.ini that controls the colors that the BSoD code uses to any of the
16 CGA colors.
System adminstrators often use "to bluescreen" or "to BSoD" as a verb, as in: "The server just BSoD'd" or "Windows 2000 doesn't bluescreen as much as NT 4 did." (This usage is unrelated to color key special effects in film, also called bluescreen.)
The Blue Screen of Death is present in all Windows operating systems since Windows version 2.0.