Operating system is a system software, which controls the function of computer after establishing a relationship between its hardware and software. The user cannot work on the computer without the knowledge of operating system. The DOS developed by Microsoft Corporation is known MS- DOS. Since it has been developed by Microsoft, therefore Ms (Microsoft) is written before DOS. The DOS developed by IBM (International Business Machines) in the year 1981 used to operate PC. That is why it was called POSTDOC. At first DOS edition 1.00 was launched by Microsoft in the market. As the computer of improved new generation arrived the corresponding versions of DOS also come in the market.
‘Boot’ means to start. Turning the computer on is called booting. Booting is of two types:
□ Cold Booting
□ Warm Booting
when you switch on the CPU, then ROM (Read Only Memory) activities a program BIOS (Basic Input Output Services), which is stored in the IC (Integrated Circuit) of the motherboard of the computer. Then BIOS and POST (Power On Self Test) check the RAM (Random Access Memory). After that, it checked peripheral devices. Peripheral devices are connected to CPU, like keyboard, mouse screen, printer etc and stores their interrupt code in the vector table. After this, it activities ROM-BIOS, BSLP (Boot Strap Loader Program), Which Search Boot Record in Disk. Boot records then searches all the three system files, IO.sys, command.com and MS-DOS.sys. If all these three files are found, then system prompt in the form of A:\> or C:\? Appears on the screen.
When these files are not available, then an error message “Non-System Disk error” appears. In the last step of Booting, computer gives message to input current date and current time. But if bat file is in or C:, then it will not ask for it. Computer will work in accordance with the instructions in auto exec.bat.
Sometimes computer stops warning and does not accept in the instructions given by the user. In such a situation, do cold booting. Simultaneously press Alt+Ctr+Del keys and Warm Booting happens, which takes lesser time tan Cold Booting. Because POST and RAM are not examined in this operation.
Feature of DOS
Following are DOS features:
□ File Management
□ Disk management
□ Memory Management
DOS follows user’s instructions. Instructions to DOS are given in the form of command. Let us know about files.