DOS (Disk Operating System) is first operating system release by Microsoft. Before Microsoft; DOS was released by IBM named IBM DOS. Bill Gates started own company Microsoft and released MS DOS 1.0. Before invention GUI Operating System (Windows) DOS’s last version was 6.22. After DOS 6.22 Microsoft never release MS DOS. MS DOS was a simple and command based operating system. There was no use of mouse in MS DOS. All commands were type able from keyboard. Some MS DOS’s famous commands are still in use in Windows Shell (Command Prompt). There were two types of commands in MS DOS.

1. Internal Commands
   
   Internet commands were built in DOS shell commands and do not need any external file. Here are some internal commands.

   DIR

   Get the list of files in current folder or directory

   CLS

   Clears current working screen of MS DOS)

   DATE

   View or change current date of system

   TIME

   View or change current time of system

   REN or RENAME

   Rename a file

   COPY

   Copy a file

   VER

   Get the current DOS version

   MD

   Create directory or folder

   RD

   Remove directory or folder if empty

   Note: All internal commands are still supported in Windows Command Prompt.
   
   
2. External Commands
   
   External commands were not part of DOS shell and need external files same like Windows Library (DLL) files. Here are some MS DOS’s external commands.
   

   DELTREE

   Remove folder including all sub folders and files

   LABEL

   View or change disk’s label name

   FORMAT

   Format the Hard Disk or Floppy Disk

   CHKDSK

   Run disk check on Hard Disk or Floppy Disk

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