The process of loading an operating

The process of loading an operating system into main memory is call booting the system. Figure 8-2 show information that is displayed during this process. The actual information displayed will vary depending on the make of the computer and the equipment installed.The following steps explain what happens during the boot process on an IBM compatible personal computer that operates using DOS.
1.When you turn on your compter, the power supply distributes current to the motherboard and the other devices located in the system unit case.
2.The surge of electricity causes the CPU chip to reset inself and look to BIOS chip for instructions on how to proceed. BIOS stands for. The BIOS is a set of instructions that provides the interface between the operating system and the hardware devices.
The BIOS is stored in a read-only memory (ROM) chip.
3. The BIOS chip begins a set of tests to make sure the equipment is working correctly. The tests, called the POST, for Power On Self Test, check the memory, keyboard ,buses, and expansion cards. After some of the early tests are completed, the BIOS instructions are copied into memory where they can be executed faster than in ROM.
4.After the POST tests are successfully completed, the BIOS begins looking for the operating systemm Usually, it first looks in diskette drive A. If an operating system disk is not loaded in drive A, the BIOS looks on drive C, the drive letter usually given to the first hard drive.
5.When the BIOS finds the operating system, it begins loading the resident portion into memory. For personal computers using a version of DOS, the resident portion is called the DOS kernel.
6.The kernel then loads system configuration information. The configuration information is contained in a file called CONFIG.SYS This file tells the computer what devices you are using, such as mouse, a CD-ROM, a scanner, or other devices. For each of these devices, a device driver program is usually loaded. Device driver programs tell the computer how to communicare with a device.
7.The kernel loads the command language interpreter. On DOS computers, the command language interpreter is called COMMAND.COM
8.COMMAND.COM loads a batch file named AUTOEXEC.BAT that performs optional tasks such as telling the system where to look for files (PATH command) and loading programs that you want to run every time you turn on your system, such as certain utility programs.
9.If you haven't specified that the computer immediately start a particular application program, the system displays a command language prompt that indicates the system is ready to accept a command from the user. If you alway want a particular application program to automatically start during the boot process, such as a word processing program or Microsoft Windows, you include the name of the program as the last line the AUTOEXEC.BAT file.