To program well, you have to know more about your hardware and DOS internals. In many Institutions hardware & software are being taught as different subjects. And people don’t know how both are related. For system programming you must know the relationship between the two. Here I will help you to understand why a programmer should know hardware & DOS internals for DOS programming.
Prelude
DOS (Disk Operating System) is the widely used operating system. It is a single-user operating system. DOS is designed to provide an easy way to use disks for storage. It is very efficient in controlling, accessing and managing the data from disk drives. The basic operations performed by DOS are regulate space allocation, keep track of files, save and retrieve files and manage other control functions associated with disk storage. Thus using DOS an interface is
made between the user and the computer. This DOS is same for all the systems. For loading this DOS to the memory BIOS, bootstrap program, diagnostic testing programs are very essential and we will discuss it in the coming sections.
BIOS
It is a program that provides link between the hardware and the operating system. It is a firmware (Firmware is a program or data stored in ROM. These are not altered by software, and are not lost when the power is turned off). Since it is stored in ROM, it is usually called as ROM BIOS. It contains many low level routines. It is responsible for basic hardware operations such as interactions with disk drives and keyboards. It also has drivers and other software that manages the peripheral devices. The basic operations performed by BIOS are
- Keyboard routine
- Video routines
- Printer routines
This BIOS program differs from system to system. For getting good results we can use BIOS functions along with the DOS functions.
Bootstrap Program
Bootstrap program is responsible for loading the operating system from the disk to the memory. When the computer is switched ON the process of bootstrapping takes place, which initializes the computer for use, by automatically clearing memory and loading the first few instructions that call other instructions in the disk (Nowadays the remaining part of the operating system resides in the hard disk itself).
The basic operations performed by bootstrap program are
It runs the diagnostics testing programs to check the status of RAM.
It makes a call to the disk for loading the operating system into the memory.
After loading the operating system, it transfers control to the operating system.
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