How does it work Boot Disk.

How does it work Boot Disk.

The personal computer can not do anything if you do not have a usable operating system - the program that allows the
PC using other programs. But before you run the operating system, the PC needs a way to carry it in
random access memory (RAM). This form is known as a bootstrap, or just boot - a small code that is part
Permanent PC.

The bootstrap has this name because it allows the PC to run something by itself, without the aid of an external operating system.
In fact, the boot operation does not do much. She has only two functions: run the self-test or POST initial
and search the hard disk for the operating system. At the end the two functions, starts the process of reading
the operating system files and copy these files to the random access memory.

Why PCs use this type of method? Why not integrate the operating system on the PC? Some computers more
specialized or more basic do. The first models, mainly used for games such as Atari 400 and 800,
and the recent LX95 palmtop Hewlett-Packard have an operating system permanently. The LX95 even includes an application,
Lotus 1-2-3, a special microchip. But in most cases, the operating system is loaded from disk by two
reasons.
Easier to update the version of the system if it is loaded from disk. When a company like Microsoft -
manufacturer of MS-DOS, the most used operating system in PCs - want to add new features or debugging
programming (bugs), it simply launches a new set of disks with the new version. Sometimes, only a single file
is inserted to correct a flaw in the operating system. It is cheaper to distribute the Microsoft DOS diskettes
to design a microchip that contains the operating system. And much easier for users to install a new DOS
diskettes to swap chips.

Another reason to load the operating system from disk is to allow the user to choose the system.
Although most PCs based on Intel microprocessors manufactured by using the MS-DOS operating systems there
alternative such as OS / 2, the DR DOS and Unix. In setting up some PCs, you can even define which operating system
will be used every time you turn on your computer.

Source: Evolution of Computers