(BSOD) Blue Screen Of Death

The Blue Screen of Death (also known as a stop error, BSoD, bluescreen, or Blue Screen of Doom) is a colloquialism used for the error screen displayed by some operating systems, most notably Microsoft Windows, after encountering a critical system error which can cause the system to shut down to prevent irreversable damage to the system's integrity. It serves to present information for diagnostic purposes that was collected as the operating system issued a bug check.

If so configured, the system will 'dump' all of its memory to a file on disk. Data in memory would then be lost but in some circumstances it could be retrievable from the dump file, a process that must be carried out by a trained PC technician.

According to Microsoft, bluescreens on NT-based Windows systems are usually caused by poorly-written device drivers or malfunctioning hardware. In the Win9x era, incompatible DLLs or bugs in the kernel of the operating system could also cause bluescreens. They can also be caused by physical faults such as faulty memory, power supplies, overheating of computer components, or hardware running beyond its specification limits. Bluescreens have been present in all Windows-based operating systems since Windows 3.1; earlier, OS/2 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, Texas, the developers described the stop screen as the Blue Screen of Death to denote the screen and the finality of the experience.[citation needed

In Microsoft Windows NT-based operating systems, the blue screen of death (displayed in 80×50 text mode as opposed to 9x/Me's 80×25) occurs when the kernel or a driver running in kernel mode encounters an error from which it cannot recover. This is usually caused by an illegal operation being performed. The only safe action the operating system can take in this situation is to restart the computer. As a result, data may be lost, as users are not given an opportunity to save data that has not yet been saved to the hard drive.

The text on the error screen contains the code of the error along with four error-dependent values in parentheses that are there to help software engineers fix the problem that occurred. Depending on the error code, it may display the address where the problem occurred, along with the driver which is loaded at that address. Under Windows NT and 2000, the second and third sections of the screen may contain information on all loaded drivers and a stack dump, respectively. The driver information is in three columns; the first lists the base address of the driver, the second lists the driver's creation date (as a Unix timestamp), and the third lists the name of the driver.[1]

By default, Windows creates a memory dump file when a blue screen error occurs. Depending on the OS version, there may be several formats this can be saved in, ranging from a 64kB "minidump" to a "complete dump" which is effectively a copy of the entire contents of physical RAM. The resulting memory dump file may be debugged later, using a kernel debugger. A debugger is necessary to obtain a stack trace, and may be required to ascertain the true cause of the problem; as the information on-screen is limited and thus possibly misleading, it may hide the true source of the error.

Microsoft Windows can also be configured to send live debugging information to a kernel debugger running on a separate computer. Windows XP also allows for kernel debugging from the machine that is running the OS. If a blue screen error is encountered while a live kernel debugger is attached to the system, Windows will halt execution and cause the debugger to break in, rather than displaying the BSoD. The debugger can then be used to examine the contents of memory and determine the source of the problem.

A BSoD can also be caused by a critical boot loader error, where the operating system is unable to access the boot partition due to incorrect storage drivers, a damaged file system or similar problems. In such cases, there is no memory dump saved. Since the system is unable to boot from the hard drive in this situation, correction of the problem often requires booting from the Microsoft Windows CD. After booting to the CD, it may be possible to correct the problem by performing a repair install or by using the Recovery Console (with CHKDSK, or fixboot).

ReactOS, an attempt at creating a free software/open source implementation of a Windows NT-compatible operating system, also features its own BSoD similar to the Windows NT/XP one.

the most famous instance of a Windows 9x BSoD occurred during a presentation of a Windows 98 beta by Bill Gates at COMDEX on April 20, 1998. The demo PC crashed with a BSoD when his assistant (Chris Capossela, who is still working for Microsoft as Corporate VP in the Information Working business unit) connected a scanner to the PC, trying to demonstrate Windows 98's support for Plug and Play devices. This event brought thunderous applause from the crowd and Gates replied after a nervous pause: "That must be why we're not shipping Windows 98 yet."[2]

The simplest version of the blue screen occurs in Windows CE except the versions for Pocket PC, which appears similar to the ones found in Windows NT/2K/XP.

The very first Blue Screen of Death happens in Windows 1.0 if a computer fails to boot up properly, it will show random letters and symbols. [3] If Windows 1.0 encounters any (MS-DOS related) critical system errors, it will instead show a Black Screen of Death