MSDOS

1
MS-DOS

• In the 1980s or early 1990s, the operating
  system that shipped with most PCs was a version
  of the Disk Operating System (DOS) created by
  Microsoft MS-DOS.

2
MS-DOS

• MS-DOS is a disk operating system for IBM
  PCcompatible computers.
• In its day, it was easily the most popular
  operating system in the world. It also is the
  basis from which Windows 9x derives its
  under-lying organization.

3
MS-DOS

• As with any other operating system, its function
  is to oversee the operation of the system by
  providing support for executing programs,
  controlling I/O devices, handling errors, and
  providing the user interface.

4
MS-DOS

• MS-DOS is a disk-based, single-user, single-task
  operating system. These qualities make it one of
  the easiest disk operating systems to understand.

5
MS-DOS

• The main portions of MS-DOS are the IO.SYS,
  MSDOS.SYS, and COMMAND.COM files.
• IO.SYS and MSDOS.SYS are special, hidden system
  files

6
MS-DOS

• The IO.SYS file moves the systems basic I/O
  functions into memory and then implements the
  MS-DOS default control programs, referred to as
  device drivers, for various hardware components.
• These include the following
• The boot disk drive
• The console display and keyboard
• The systems time-of-day clock
• The parallel and serial communications port

7
MS-DOS

• The MSDOS.SYS file provides default support
  features for software applications.
• These features include the following
• Memory management
• Character input and output
• Real-time clock access
• File and record management
• Execution of other programs

8
MS-DOS

• The COMMAND.COM command interpreter accepts
  commands issued through the keyboard, or other
  input device, and carries them out according to
  the commands definition.

9
MS-DOS

• When DOS runs an application, COMMAND.COM finds
  the program, loads it into memory, and then gives
  it control of the system. When the program is
  shut down, it passes control back to the command
  interpreter.

10
MS-DOS

• The remainder of the operating system is
  comprised of utility programs to carry out DOS
  operations, such as formatting disks (FORMAT),
  printing files (PRINT), and copying files (XCOPY).

11
MS-DOS

• When MS-DOS was developed, it was designed to be
  a simple, stand-alone, operating system. To that
  end, it didnt contain any network software,
  except SHARE.EXE.
• SHARE.EXE was designed as an add-on to popular
  networking software that allowed two users to
  edit the same file at the same time on a network.

12
MS-DOS

• Without SHARE.EXE , when a second user tried to
  open a file that the first user had opened, they
  got an error message. With SHARE.EXE installed,
  when the second user tried to open the file, they
  received a message saying that the file was being
  used by someone else and offering to provide a
  copy of the file.

13
MS-DOS

• Another aspect of networking with MS-DOS is that
  DOS can run client software for Novell and
  Microsoft networks. Most client software for DOS
  falls into the category of redirection software.
  This software redirects requests bound for local
  resources out to network resources.
• For example, with network client software
  installed, you could point a DOS drive letter to
  some disk space on the network. When you saved a
  file to that drive letter, you were really saving
  that file to a server. But, as far as DOS was
  concerned, it was accessing a local drive letter.

14
MS-DOS

• MS-DOS Versions
• Next we will look at the evolution of the MS-DOS
  operating system and will examine the major
  changes in microcomputer architecture and
  standards that are reflected in each revision.

15
MS-DOS

• MS-DOS 1
• The original version of MS-DOS was, to put it
  mildly, a no-frills operating system. It had no
  provisions for networking, did not include any
  sort of graphical shell program, and had limited
  ability to manage system resources. Approximately
  a year after the release of DOS 1.0, a
  revisionDOS 1.1added support for double-sided
  320KB floppy drives.

16
MS-DOS

• MS-DOS 2
• In early 1983, IBM introduced the IBM PC XT. The
  XT featured a 10MB hard drive, a serial
  interface, and three additional expansion slots.
  It also had 128KB of RAM and a 360KB floppy drive
  (40KB more capacity than that of single-sided
  floppies on the previous PC) and could support a
  10MB internal hard drive.

17
MS-DOS

• MS-DOS 3
• With DOS 3.0, released in summer 1984, Microsoft
  continued to include additional DOS features and
  to support more powerful hardware. DOS 3.0
  supported hard drives larger than 10MB, as well
  as enhanced graphics formats.
• Three revisions3.1, 3.2, and 3.3provided
  additional innovations.

18
MS-DOS

• Version 3.1 was notable because it featured the
  first DOS support for networking. The IBM PC
  Network was a simple local area network structure
  that was similar to todays workgroup networks.

19
MS-DOS

• DOS 3.2 introduced the XCOPY command, enabling
  the user to identify more than one file at a time
  to be copied, and it made important modifications
  to other DOS commands. It was also the first
  version to support IBMs Token Ring network
  topology and the first to allow for 720KB 3.5
  Inch floppies.

20
MS-DOS

• Version3.3, introduced in 1987, offered
  additional enhancements to numerous existing
  commands and introduced support for 1.44MB floppy
  disks. Logical partition sizes could be up to
  32MB, and a single machine could support both a
  primary and a secondary partition on each disk.

21
MS-DOS

• MS-DOS 4
• By 1988 it was apparent that the wave of the
  future was the graphical interface, and DOS 4
  provided users with the DOS Shell, a utility much
  like the Windows File Manager. Actually, DOS
  Shell was simply a scaled-down version of Windows
  that allowed users to manage files, run programs,
  and do routine maintenance, all from a single
  screen. The DOS Shell even supported a mouse.

22
MS-DOS

• MS-DOS 5
• There were several important features introduced
  in the 1991 release of DOS 5.0. First of all, the
  ability to load drivers into reserved (upper)
  memory was a relief to those people who were
  constantly running out of conventional memory.
  This feature allowed more complex DOS programs.
  Several software utilities made their debut. The
  most commonly used utility introduced at this
  time was EDIT.COM. Also added were QBASIC.EXE,
  DOSKEY, UNFORMAT, and UNDELETE.

23
MS-DOS

• MS-DOS 6
• Released in 1993 to excellent sales, DOS 6.0
  offered a number of new commands and configurable
  options. Another enhancement in DOS 6.0 was
  EMM386.EXE, which allowed the system to pool
  extended and expanded memory. DOS 6.0 has
  subsequently been revised a number of times. As
  of this date, DOS 6.22 is the most current MS-DOS
  version available as a stand-alone operating
  system.