A Blue Screen of Death (also known as a stop error, BSoD, bluescreen, or Blue Screen of Doom) is an error screen displayed by certain operating systems, most notably Microsoft Windows, after encountering a critical system error which can cause the system to shut down to prevent damage.
Bluescreens on NT-based Windows systems can be caused by poorly written device drivers or malfunctioning hardware. In the Win9x era, incompatible DLLs or bugs in the kernel of the operating system can also cause bluescreens. Sometimes, when the CPU is hit in any way, the computer may restart and show the BSoD.
Bluescreens can also be caused by physical faults such as faulty memory, mains power supply voltage variance or spikes in conjunction with or magnified by power supply unit voltage rating not matching the mains supply (such as a 220V PSU attached to a 240V mains outlet), the power requirements of the computer exceeding the capacity of the PSU, overheating of components, intermittent power to hard disk drives or other parts, faulty hardware, or hardware running beyond its specification limits. Bluescreens have been present in all Windows-based operating systems since Windows 3.1; earlier, OS/2 and MS-DOS suffered the Black Screen of Death, and early builds of Windows Vista displayed the Red Screen of Death after a boot loader error.
The term "Blue Screen of Death" originated during OS/2 pre-release development activities at Lattice Inc, the makers of an early Windows and OS/2 C compiler. During porting of Lattice's other tools, developers encountered the stop screen when NULL pointers were dereferenced either in application code or when unexpectedly passed into system API calls. During reviews of progress and feedback to IBM Austin, the developers described the stop screen as the Blue Screen of Death to denote the screen and the finality of the experience.