Booting can simply be defined as the process of turning on a computer. Generally in computers with Microsoft Disk Operating System (MS-DOS), this process, two files, i.e. IO.SYS and MSDOS.SYS are used. Firstly, these files are hidden and are invisible to DIR command. This means that we cannot see them with DIR command in MS-DOS. These files are called system files. COMMAND.COM is the command interpreter. All these files are stored on a floppy disk or on a hard disk and therefore, they must be loaded into memory prior in order to be used. Thus, in broad sense, booting can be defined as the process of loading system files and COMMAND.COM from a disk into computer’s Random Access Memory (RAM). Generally, booting can be classified into two types, they are:
- Warm Boot: When the user is working on the computer and wishes to reboot or restart the computer, i.e. he wants to wipe or erase all the programs in RAM and clicks on restart button, the computer begins to search for system files in the disks and loads them into the RAM. This process is called warm boot.
- Cold Boot: When the computer is in off state and the user presses the power switch of the computer to switch it on, the computer reads the RAM and searches for system files of Disk Operating System from different drives. As soon as it finds the system files, the files reside into the computer’s memory and computer begins to work. This process is called cold boot.
Now, we will clarify the different functions and features of the different system files. They are:
- IO.SYS: IO.SYS is a system file which helps to handle input or output operations in computers. It permanently resides in the memory as long as the computer’s power is on. This program remains in the memory even if we change our application software in the computer.
- MSDOS.SYS: This is a program which is used by application programs. It contains special sub-prgrams which help to make common operations easy for the program.
The two files mentioned above are loaded into memory every time we start computer with a special program called boot record.
- COMMAND.COM: This is the program which accepts and understands the commands that we enter using the above two files to give the desired or required result. In other words, we can also take COMMAND.COM as a command interpreter.