Disk Operating SystemDOS

1
Disk Operating System(DOS)

• Disk Operating System
• Was originally created to manage files on disks
• standard operating system for IBM PCs
• Successive releases incorporated more devices COM
  ports, CD-ROMS, etc.
• Originally developed by Microsoft for IBM, MS-DOS
  was the standard operating system for
  IBM-compatible personal computers
• A simple operating system
• 16-bit operating system
• does not support multiple users or multitasking

2
Office Analogy

• Consider an office area
• You - like a computer processor - the device that
  performs the work
• Workspace/Desk - like memory(RAM)
• storage space (filing cabinets, drawers, etc.) -
  like permanent storage(disks)
• tools (pencils, pens, rulers, calculators, etc) -
  like IO devices
• A sample task to work on a file, go to a drawer,
  pull out the file, open the file file the
  document you need and put on your desk - like the
  OS pulling a program from disk, loading it in
  memory, and executing it
• The basic functions of an operating system(DOS)
  are
• File management - analogous to the file cabinet
  and its use
• Working with the Files Devices - analogous to
  picking up and preparing to use a calculator or
  some other tool
• Configuration of your working environment -
  analogous to shifting your desk around to suit
  you better

3
DOS Command Shell

• The command shell is the program that executes
  operating system commands
• interactive
• i.e. a means to interact with the OS
• waits for user inputs
• verifies it is correct(syntax checking)
• passes the command to the operating
  system(command processor) to be executed
• The command prompt
• C\MYDIR\gt
• Why learn the shell - cant I do everything from
  Windows?
• In Windows NT, some admin commands can only be
  done from the shell

4
DOS Commands

• How the user talks to DOS
• Syntax
• DOS requires commands in a specific format, for
  DOS this is
• command_name parameters switches
• parameters - what you want the command to act on
• switches - turn on optional command functions
• ex. dir a /p - directory command on disk a
  switch /p(pause)
• Dont know the exact command syntax? Use /?
  Switch
• ex. dir /? - gives parameters and switches
• Enter command at the prompt(gt)
• if syntax is correct, it is executed when you
  press Enter
• DOSKEY
• keeps a history of executed commands so you can
  use arrow keys to retrieve them

5
Formatting Disks

• You must format a disk before it can be used
• most floppy disks sold today are preformatted
• The DOS format command prepares a disk by
• Creating a map on the disk, magnetically
  marking tracks sectors
• Checking the disk for defects
• identifying bad sectors that should not be used
• Creating a root directory
• Setting up the File Allocation Table(FAT)
• the storage table that identifies the files on
  the disk and where they are located(at a minimum)
• recall that formatting doesnt erase disk data -
  just the FAT
• Bootable disk
• a disk that has the operating system files
  necessary to start DOS
• to create a bootable DOS disk, format with /s
  switch

6
DOS File Management Commands

• DIR
• Directory Command - lists all the files in a
  directory/folder
• DIR A more
• CD
• Change Directory - allows you to move around the
  directory tree
• CD C\WINDOWS\TEMP
• MKDIR
• Make Directory - create a new directory/folder
• MKDIR C\TEMP\MYNEWDIR
• COPY
• copies a file to a new location/name
• COPY SOURE.TXT DEST.TXT
• MOVE
• moves the file to a new location/name(deletes
  original)
• DEL
• removes the file
• DEL BOGUS.TXT

7
Working with Files

• Recall 2 types of files used by OS
• binary(raw bytes) text(ASCII characters)
• How does DOS tell the difference?
• Usually by the files extension (the part after
  the . in the name)
• ex.
• .txt, .bat text files
• .exe, .com binary(executable) files
• Text files can be viewed from DOS with the TYPE
  command
• type myfile.txt /p

8
Miscellaneous

• Wildcard Characters ?
• matches any group of characters
• COPY .TXT A - copies all files ending in .TXT
  to A
• COPY . A - copies all files from the current
  working directory to A
• ? Matches any letter
• current working directory
• the directory the DOS command shell is currently
  in
• DISKCOPY
• copies an entire disk at a time
• DISKCOPY A A to copy a floppy