Working with DOS
MS-DOS is a command user interface operating system. Loading operating system files into main memory is called booting up of the computer. A file is a collection of logically related information. Each file stored on the system is given a name. Two special characters, question mark and asterisk are called wildcards in DOS.DOS internal command is stored in the system memory and loaded from the command.com. POST checks for the integrity of all component. If any component is found faulty, an error message is displayed. A chip ROM-BIOS is read and executed. DOS files are first searched in drive A, if not found then in drive C. First IO.SYS file is loaded into the main memory & then MSDOS.SYS. After that certain internal tables are initialized. CONFIG.SYS file is being searched from the drive (contains OS file) and if found then the computer system is configured according to it. Now, the COMMAND.COM is loaded into the main memory. AUTOEXE.COM file will be searched for the COMMAND.COM and if found, all its instructions will be executed.
ver command tells about the version of the dos installed in the computer. The dir command is used to view the content of directories present in the system. Drive from which the DOS has been loaded becomes the default drive or active drive. First level in hierarchical directory system is root directory. After booting, root directory is the default directory.