A system failure can occur because of a hardware failure or a severe software issue, causing the system to freeze, reboot, or stop functioning altogether. A system failure may or may not result in an error being displayed on the screen. The computer may shut off without warning and without any error message. If an error message is displayed, it often is displayed as a Blue Screen of Death error on Windows computers.
System failures may result from a hard drive with bad sectors, causing the operating system to not be able to read data from the hard drive. A failing motherboard can cause a system failure because the computer is not able to process requests or operate in general. A bad processor can and usually causes a system failure because the computer cannot operate if the processor is not working properly or at all. A bad RAM (random-access memory) chip can also cause system failures because the operating system is not able to access data stored on the RAM chip.
System failures due to software issues can occur if the issue in the software, such as a bad line of code, is severe enough. The system failure and subsequent computer shut down occurs as an attempt to prevent damage to other software or the operating system.