Basics Of MS-DOS (Internal & External Command)

DOS Commands

DOS Commands are instructions to perform tasks on files and directories very useful to Windows users. DOS commands are case insensitive. And as you already know, file is the area where we store group of information or data, and collection of group of files is called a directory.

In MS-DOS the file name follow 8dot3 format and is divided into two parts – primary name and secondary name. Primary name is up to 8 characters long and secondary name is up to 4 characters with dot. For example, in the file-name Logo.jpg, Logo is the primary name and .jpg is the secondary name. Secondary names are fixed for particular type of file, meaning for system files the secondary name is designated as .sys, for text files it is .txt and so on. To name a file or directory special characters like < > , . / * ? | & Space are not allowed. Here is the list of some of the important types of files with their default secondary names:

DOS Commands are divided into 2 types:

1. Internal Commands These are for performing basic operations on files and directories and they do not need any external file support.
2. External Commands These external commands are for performing advanced tasks and they do need some external file support as they are not stored in COMMAND.COM

There are also Batch commands or Batch files which are text files that contain a list of internal and/or external commands which are executed in sequence when the batch file is executed. AUTOEXEC.BAT gets executed automatically on booting.

In MS-DOS, keyboard shortcuts involving handy ones like Functional keys, arrows, pipe character (” | “), asterisk (*), ?, [] and ESC are of great help for recalling to searching to clearing command line etc., Here are few of them:

• UP (↑) and DOWN (↓) arrows recall previously entered commands.
• ESC clears the present command line. It abandons the currently construct command and the next prompt appears.
• F1 or → retypes one character at a time from the last command entry from the current cursor position.
• F2 retypes all characters from the last command entry up to the one identical to your next keystroke. It asks you to enter char to copy up to and retypes the last command up to that char.
• F3 retypes all remaining characters from the last command entry.
• F4 stores all characters beginning at the first match with your next keystroke and ending with the last command entry.
• F5 or F8 keys give all the previously typed commands.
• F6 places a special end-of-file code at the end of the currently open file. Sometimes referred to as Ctrl+z or ^z.
• F7 key displays command history and ALT+F7/ESC hides it.
• F9 is used to select a command by number. Just enter the command number and it fetches the command line for you.
• Pipe character (” | “) combines several series of commands or programs inter-dependent.
• Name enclosed within [] indicate a sub-directory.
• Asterisk (*) is used to represent zero or more any characters.
• ? is used to present zero or single character.

MS-DOS commands perform tasks like:

• Manage files and directories
• Maintain Disks
• Configure Hardware and Networking
• Optimize the use of memory
• Customize MS-DOS