The BIOS then locates software held on a peripheral device (designated as a 'boot device'), such as a hard disk or a CD, and loads and executes that software, giving it control of the PC. When the PC starts up, the first job for the BIOS is to initialize and identify system devices such as the video display card, keyboard and mouse, hard disk, CD/DVD drive and other hardware. The primary function of the BIOS is to load and start an operating system. The BIOS of a PC software is built into the PC, and is the first code run by a PC when powered on ('boot firmware'). In Windows, when the pointer goes from the hour glass to the normal pointer, the operating system has been loaded and all the subsystems are synchronized and ready for user requests to process data. From the time we switch on the computer to the booting process, a series of the following events occur. The booting process of DOS begins with the examination of the first sector of a diskette or hard disk is loaded into memory.
For example, Macs allow users to run OS X, Windows, and Linux using the Boot Camp boot manager that comes as a OS X utility. This allows for multiple boots to allow different operating systems to be loaded and used on the same computer. Learning objective: Describe the events of the booting sequenceĮvery time you turn on your computer, its as if its the first time your computer has ever been turned on since there are no instructions or data in memory. Operating Systems Architecture Operating Systems Architecture
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