Lectures of Chuck Kelly,
Monroe County Community College

Last update: 9/27/2000
 
 

General Stuff

An operating system (OS) is a "middle-man". Its role is to provide a layer of separation between the PC hardware and the application software or user (See Figure 1 ) and to facilitate user interaction with the hardware. The interaction may be with application software or users. When application software needs to use part of the PC hardware it goes through the OS to gain access. For example when a word processing application needs to print a document, it gains access to the PC’s printer by sending the print requests through the OS.

The OS needs to play "middle-man" because the PC Hardware is in a constant state of change. It would be practically impossible for Application Software developers to keep up with all of the different hardware their software might encounter. By using the OS as a buffer between applications and hardware it is only necessary to change the OS when the PC hardware changes. All of the applications continue to work without modification.

In order to facilitate changes in the hardware the OS has another layer of software separating it from the hardware. This software layer is comprised of Device Drivers. (See Fig. 2).

A device driver is software written to allow the OS to control a particular piece of hardware. Device drivers are typically provided by the hardware manufacturer.

History

The first PC OS is often cited as being PCDOS (Personal Computer Disk Operating System). Actually the proper statement would be, the first OS for the IBM ® PC was PCDOS. The first PC or Personal Computer was not even made by IBM nor did it run DOS. The first commercially produced PC was the Altair. It was sold in kit form in the mid 70’s. Shortly after that, Apple Computer introduced the Apple PC which used an OS called DOS and then ProDOS and then the Macintosh PC which used MacOS. Around 1980 is when IBM built the first PC. The term PC has since become synonymous with the IBM PC and compatible computers.

The first versions of PCDOS were designed for PCs that had 360KB floppy drives, 256K of RAM and no hard drives. Needles to say they were very limited in power when compared with today’s choices.

User Interface

DOS uses a Command Line Interface (CLI). With a CLI the user enters commands for the OS from the keyboard and the OS responds with text messages on the display device. CLIs are typically more difficult to learn and use because they are less intuitive and require the user to memorize commands.

The first PC OS to support a Graphical User Interface (GUI) was Windows ®. Actually, the first versions of Windows were not really an OS. They were GUI front ends for DOS. This means DOS was still the underlying OS and Windows simply presented the user with a different means of interacting with DOS. The earliest versions of Windows were not very popular. Not until Windows 3.0 did the GUI software begin to catch on.

A GUI allows users to interact with the OS by manipulating menus and icons on the display. This is typically done with some sort of pointing device such as a mouse or trackball. Graphical interaction is much more intuitive and therefore easier to learn than CLI software.

Multitasking, Task-switching, and Multithreading

Multitasking is the ability of an OS to run more than one program at the same time. Multitasking is available in two basic flavors: cooperative and preemptive.

In cooperative multitasking the OS gives control to an application and the application is responsible for releasing control back to the OS so the next application can run. If each application is "Well behaved" then all of the applications will appear to be running at the same time. The danger with cooperative multitasking is that while an application is running it has total control of the system. If the running application should crash or fail to return control to the OS then all of the applications and the OS will stop working.  Windows 3.1 uses cooperative multitasking.

Preemptive multitasking is controlled by the OS. Each application is given a small slice of time to run. After an application's time is up the OS interrupts the application and then gives the next application a small slice of time to run. Because the slices of time are small (fractions of a second), and the OS switches between all of the applications very quickly, all of the applications appear to be running at the same time. Preemptive multitasking is safer than cooperative multitasking because the OS controls when each application runs. Windows 9x/NT uses preemptive multitasking. Windows 9x also supports cooperative multitasking to make it compatible with older applications.

Task switching was first introduced in DOS with DOSSIER. Task switching simply places multiple applications in memory at the same time but only one application is actually running. The user can quickly switch between applications without the need of any disk access. In the days when floppy drives were the norm, task switching could greatly increase a user's productivity. Today it has limited usefulness.

Multithreading is a form of multitasking that is contained within a single application. A single application may have its program split into more than one part and these parts may all be running at the same time.

Windows^® 9x

Windows 95 was the first GUI OS for the PC that did not require a separate installation of DOS. Several versions of Windows 95 were released with such designations as OSR2 and Rev.C. The latter releases contained various bug fixes and support for new types of hardware. Then came Windows 98 and Windows 98 (Second Edition).

Windows^® NT/2000 Professional

Windows NT/2000 Pro is a more stable and robust operating system than Windows 9x however, it is not compatible with all of the older windows applications. It is targeted at the professional user where power and stability are more important that backward compatibility with older applications. The user interface and general operation of NT 3.51 is very similar to Windows 3.1, NT 4.0 looks like Windows 95.

Windows^® Me

http://www.microsoft.com/windowsme/guide/default.asp

The newest contender is Windows Me (Millenium Edition). Me is designed for the home user. It promises to be more compatible with older applications than NT/2000 Pro. Me is the successor to Windows 98.
 
 

Windows Details

The Desktop

• The contents of the desktop reside in the directory: C:\windows\desktop
• Files and folders added to this directory will appear on the desktop
• Tip! To close multiple windows use Shift + Click on Close Box. This will close all windows opened up to the root of the current branch?

Using Print Screen

• Pressing the Print Screen key sends a copy of the current desktop to the clipboard
• Pressing Alt + Print Screen sends a copy of the current window to the clipboard

• Most Windows objects have properties
• To view an objects properties, right click on the object and select properties from the shortcut menu

{Demonstrate changing date and time}

Viewing System Properties

• Right click on My Computer and select Properties
• The General tab displays the Version, Registration, CPU, and RAM information
• The Device Manager tab displays information about hardware devices

{Change the driver for the video card}

Using Online Help

{Demonstrate Windows Help}

Changing Desktop Properties

{Demonstrate}

Adjusting Screen Resolutions

{Demonstrate}

Using Accessibility Options for Employees with Disabilities

• To install the Accessibility Options
• From the Control Panel double-click Add/Remove Programs
• Select the Windows Setup tab
• Choose the accessibility option desired and click OK.

Managing Drives, Folders, and Files

• When files or folders are dragged from one drive to another the default operation is copy.
• When files or folders are dragged from one location on a drive to a different location on the same drive the default operation is move.
• Use Right-Drag to get the option to pick copy or move.
• Press Ctrl while dragging to force a copy.
• Press Shift while dragging to force a move.
• A maximum of 75 files may be placed on the root of a floppy disk.

Changing Your View of Files

{Quickly demonstrate the different ways files can be viewed}

Formatting a Disk

{Explain tracks, cylinders, sectors and clusters}

{Demonstrate a format}

Copying a Disk

{Demonstrate}

{Also demonstrate viewing drive properties}

Shortcuts

• Provide rapid access to programs, folders and devices
• Deleting a shortcut does not delete the original program or folder
• The program or folder pointed to by the shortcut may exist on a different disk
• Shortcuts do not track items that are moved or deleted
• Use Right-Drag to create

(Demonstrate checking the shortcut properties}

Using Find to Locate Files

{Demonstrate}
 
 

Using Windows Explorer

{Demonstrate}

Windows 9x Setup
 

Steps for a new installation:

• Create a primary DOS partition on the hard disk with FDISK. With Win95 OSR2 and newer you can choose to use FAT32 instead of FAT16 when creating the partition. FAT32 supports drives larger than 2GB. With FAT16 if the hard drive is larger that 2GB it is necessary to partition it into more than one logical drive. (Caution! Partitioning a drive with FDISK will erase all of the files on the drive).
• Format the newly partitioned drive.
• Copy the WIN9x directory from the Windows CD to drive C:. The WIN9x directory contains what are commonly referred to as CAB files. The CAB files contain all of the information necessary to install Windows. Once the CAB files are copied onto the hard drive the Windows CD is no longer necessary.
• Change directories to the WIN9x directory and run SETUP.EXE to install Windows.
• When Windows is installed using this method the Windows CD will never be required when system updates are made in the future. The only disadvantage is the small amount of hard disk space that is required for the CAB files.
• When prompted for the Windows serial number here is a number that always works for Win95/98:
• 010000-OEM-0123456-010000

Steps for re-installing:

• Right click on "My Computer" and select properties. Under the General tab record the serial number used when Windows was installed.
• Copy the WIN9x directory from the Windows CD to drive C:.
• Change directories to the WIN9x directory and run SETUP.EXE to install Windows.
• When Windows is installed using this method the Windows CD will never be required when system updates are made in the future. The only disadvantage is the small amount of hard disk space that is required for the CAB files.
• When prompted for the Windows serial number enter the number you recorded. (Important! Windows will not install if you use a different serial number).

Updating a current installation to point to CAB files:

Instructions for editing the registry in Win95/98 to change where Windows will look for CAB files.

1. Open regedit
2. Navigate to: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Setup.
3. In the right pane, next to SourcePath, you'll see the path D:\win95 (or wherever you installed Windows from originally).
4. Change it to the folder to which you copied the CAB files--right-click SourcePath, select Modify, type the correct path on the Value data line, and click OK.
5. Reboot your system, and Windows 9x will never complain that it can't find the CD again.

{Demonstrate a Win95 install}

Dual Boot Configuration

• Install MS-DOS first
• Select Dual-Boot installation from Win9x
• Several DOS files will be renamed.
• IO.SYS, MSDOS.SYS, CONFIG.SYS and AUTOEXEC.BAT will be renamed to *.DOS.
• In MSDOS.SYS (the Win95 file) the [options] section should contain the line BootMuiti=1.
• Pressing F8 when the Starting Windows 9x message appears will bring up a menu that will allow you to boot to the previous operating system. Pressing F4 will boot MS-DOS directly.

• Drive A: must be a 3.5"
• With Win 95 files are not included to enable access to the CD-ROM drive. You must add these yourself.
• Can be created during installation or from the control panel.

• The PC BIOS’s must be set to enable the floppy boot.

• Press F8 during startup
• Normal - The default Windows boot process
• Logged (BOOTLOG.TXT) - Creates a text file description of the boot process.
• Safe mode - Only loads device drivers for the mouse, keyboard, and video display
• Bypasses startup files
• Use this option if Windows fails to boot. Booting in Safe mode may cause Windows to rebuild damaged files and reconfigure itself.
• Step-by-step - Allows skipping individual lines in Config.sys and Autoexec.bat.

• Click the Start button then Settings then Printers.
• Double-click Add Printer
• Follow the steps in the Add-Printer Wizard

• Click the Start button then click Help.
• Click the Index tab then type "trouble".
• In the index list select the type of Troubleshooter you want, then click the Display button.
• Follow the steps and suggestions.

• To work properly your computer must include the following:
• Plug and Play BIOS
• Plug and Play Devices

• Plug and Play OS

{Note! It is important to keep a record of a computer’s configuration.}

• Right-click My Computer, the click Properties.
• Click the Device Manager tab.

Understanding Serial and Parallel Ports

• Serial ports send data one bit at a time and require fewer wires.
• Parallel ports send data eight bits at a time and require more wires
• Serial ports allow for bi-directional data transfers, Most parallel ports support bi-directional data transfers but with less than eight bits of returning data.
• IRQ - Interrupt Request
• Input/Output Range

• Windows 9x assigns names to each of the devices in a computer, including the ports as follows:

A: Drive A First floppy disk drive
B: Drive B Second floppy disk drive, or first floppy disk drive (if there is not second drive)
C: Drive C First hard disk drive

NUL Null device Bit Bucket

The Importance of Backing Up Files

• Device failure

• Virus infection
• User errors
• Disaster

• Tape drives

• CDR or CDRW

• How often
• What to backup
• Full
• Incremental
• Includes only new files or those files that have changed since the last full or incremental backup

• Differential
• Includes all new and modified files since your last full backup.

Using Microsoft Backup

{Assignment

Using ScanDisk

• ScanDisk checks and fixes the following:
• FAT
• folder structure
• filing system
• long filenames
• physical surface of the disk
• compressed volume files
• Types of errors that are detected
• Lost clusters - a cluster that contains data but is not associated with a file.
• Cross-linked file - a file that contains a cluster that is associated with more than one file.
• Invalid filenames
• Integrity of compressed volumes

Undeleting Files

Files deleted (not in the recycle bin) may be recoverable with the MS-DOS undelete command.

Defragmenting Disks

* Describe disk fragmentation

{Demonstrate}

Checking the Status of a Disk’s Fragmentation

My Computer, Properties, Tools tab

Object Linking and Embedding

• Linked objects store the name of the file that contains the original object. Each time the file is opened the link is checked to see if the object needs to be updated. {Demonstrate this with Wordpad, Click Insert on the menu bar, then click Object, Click Create from File, then click the Link check box…}
• Embedded objects have information that identifies the application that produced the original object.

peer-to-peer

• Windows 95/98 has built-in support for peer-to-peer networking.

• Windows 95/98 includes client software for several networks
• You might want to check for newer client software from the NOS vendor

Control Panel, Networks

{Demo installing network components}

Identification tab

The Workgroup names should be the same for easy access. For Direct Cable Connection they must be the same.

{Demonstrate direct cable connection}

{Demonstrate using Find to locate a computer on the network.}

Set up a peer-to-peer network using Windows 9x.     <- Click for details.

This assignment will be graded! Turn in the following:

1. A brief written description of the procedure you followed to create the menu entries.
2. A screen capture similar to the image below. (You should reduce the size of the image so it will fit on one page.)
3. Have me verify the operation of the menu on your computer and initial your printed image.

The finished result should look something like this:

The Registry

The Registry is a database that contains configuration information about Windows and installed applications. Entries into the registry are performed automatically by Windows and applications and generally, you should not attempt to modify the registry directly. In some cases the registry can become corrupted and interfere with normal system operation. Regedit is a tool included with Windows that is used to view and edit the registry.

Registry Lab     <- Click for details.