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An Overview of the PC. PC and DOS Essentials. The Components of a PC. 1981 - The Key Year The IBM PC The Intel 8086 DOS All versions of these items have been obsessed with backwards compatibility ever since!. WINDOWS. DOS. HARDWARE. The Operating System DOS and Windows.

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an overview of the pc

An Overview of the PC

PC and DOS Essentials

the components of a pc
The Components of a PC
  • 1981 - The Key Year
    • The IBM PC
    • The Intel 8086
    • DOS
  • All versions of these items have been obsessed with backwards compatibility ever since!
the operating system dos and windows




The Operating SystemDOS and Windows
  • DOS, the operating system acts as a link between your PC hardware and your applications
  • Windows 3.x is a further layer built on top of DOS
  • Windows 95 is to a large extent independent of DOS
storage devices
Storage Devices
  • Floppy disks (diskettes)
    • Slow but convenient
    • Hold only small amounts of data (1.44 MB)
  • Hard disks
    • Fast
    • Relatively cheap
    • Hold large amounts of data
  • Tape drives
    • Excellent for back-ups
  • CD-ROMs
    • Excellent for storing data as reference material
    • A convenient method for installing programs, such as Microsoft Office
the serial and parallel ports
The Serial and Parallel Ports
  • Parallel communication
    • Faster than serial communication
    • Used to connect the PC to a printer
  • Serial communication
    • Slower, used for connection to a modem
the cpu central processing unit
The CPU (Central Processing Unit)
  • The CPU is responsible for all calculations performed within the PC
  • It determines how fast the PC will run and what systems will run on it
  • Additionally, it gets involved in a host of other activities, such as overseeing the transfer of data from the hard disk into RAM
the rom bios and the cmos ram
  • The ROM-BIOS
    • Read Only Memory - Basic Input Output System
    • Interface between DOS and the PC hardware
  • The CMOS-RAM
    • Complementary Metal Oxide - Random Access Memory
    • A read/write chip
    • Stores the system configuration, time and date as well as the power-on password (if you have set one)
pc interrupts
PC Interrupts
  • 16 hardware interrupts
  • Allows items within the PC to signal to the CPU that they require attention
  • Items must not use the same interrupt line
  • Use the MSD command to view interrupt usage
  • When a new card is installed into a PC you must ensure that it does not try to use an interrupt that is already in use
dma direct memory access
DMA (Direct Memory Access)
  • DMA was introduced in 1981 with the release of the IBM PC
    • VERY SLOW!
  • The original PC was based on the Intel 8086 CPU, which at the time was considered an OK sort of chip, running at a reasonable speed
    • To help out the CPU, the DMA was responsible for moving information from the hard disk or floppy disk into memory, thus by-passing the CPU. This increased throughput and performance
types of bus architecture
Types of Bus Architecture
  • ISA (Industry Standard Architecture) is the original PC bus architecture, introduced in 1981
  • MCA (Microchannel Architecture) was introduced by IBM in 1987 and eliminated many of the ISA design bottlenecks
  • EISA (Extended Industry Standard Architecture) was introduced in 1989
  • Plug and Play is the latest solution and allows automatic hardware configuration
plug and play
‘Plug and Play’
  • Provides a mechanism for automatically configuring any items you add to your PC
  • Requires three elements to work successfully
    • The operating system must be Plug and Play aware
      • Windows 3.1 is not Plug and Play aware, Windows 95 is
    • The ROM-BIOS must be Plug and Play aware
    • The cards themselves must be specially designed to be Plug and Play aware
getting help within dos and windows
Getting HELP Within DOS and Windows
  • Help in DOS is limited
    • HELP
    • command /?
    • HELP command
  • Most Windows applications (and Windows itself) contain tutorials, which are very useful for new users
    • As later versions of applications are released, the Help files are often modified to give improved information concerning tips and tricks
    • Context-sensitive Help should be invoked when F1 is pressed
directories and files

Directories and Files

PC and DOS Essentials

what are directories
What are Directories?
  • A convenient way of dividing up your hard disk
  • Each application can be kept in it’s own directory
    • The root directory is called CD\
    • A single . represents the current directory
    • A double .. represents the parent directory
manipulating directories under dos
Manipulating Directories Under DOS
  • Directory commands include:






Please take care



manipulating directories using the windows file manager
Manipulating Directories Using the Windows File Manager
  • Run the File Manager program, by double clicking on the File Manager program icon, located within the Main group
the dir command
The DIR Command
  • Switches include:
    • /w
    • /p
    • /s
    • /?
what are files
What are Files?
  • A file is a collection of information contained in a single unit, stored on disk
  • The DIR command displays a list of files contained in the current directory (the current directory is the directory you are in at the time)
file naming conventions
File Naming Conventions
  • There are very strict rules governing the naming of files
  • A file name can be up to 8 characters, with a 3 character file extension. You cannot use spaces (produced by pressing the spacebar) within a file name
  • File names, must not contain the following characters:-

\ | * ? < > +

  • You can use the underscore character
    • This is often useful for making a file name more readable. You can use numbers as well as letters
internal vs external dos files
Internal vs External DOS Files
  • External DOS files are held on the disk, and loaded into your computers memory (RAM) only as and when required
  • Internal commands are pre-loaded in your computers memory (RAM) when you switch on a DOS-based computer
creating text files edit vs copy con
Creating Text Files - EDIT vs COPY CON
  • COPY CON is a useful technique for creating small text files
  • Edit is useful for editing existing files or creating large complex text files
renaming deleting and undeleting files
Renaming, Deleting and Undeleting Files

Give me my

files back!

  • DEL
    • Deletes files
  • REN
    • Renames files
    • Undeletes deleted files

Beware of accidental

file deletion!

copying and moving files under dos
Copying and Moving Files Under DOS
  • COPY
    • Internal command
    • Copies files
    • External command
    • More flexible than copy
  • MOVE
    • External command
    • Only works within a disk, not between disks

Everything well organized!

copying and moving files using the windows file manager
Copying and Moving Files Using the Windows File Manager
  • Open the File Manager
  • Click on the File drop-down menu
  • Select the Copy or Move command
viewing and finding files within dos
Viewing and Finding Files Within DOS
  • View with the TYPE command
  • Use DIR/s to find
viewing and finding files using the windows file manager
Viewing and Finding Files Using the Windows File Manager
  • Open the File Manager
  • Click on the File drop down menu
  • Select the Search command
  • Double click on an associated file to view the file

Associated files

manipulating file attributes
Manipulating File Attributes
  • Attributes
    • Read Only
    • Archive
    • System
    • Hidden
  • Use of ATTRIB
    • R Read-only
    • A Archive
    • S System
    • H Hidden
  • In Windows manipulated via the File Manager
    • File/Properties
disk fundamentals

Disk Fundamentals

PC and DOS Essentials

types floppy disks diskettes and hard disks
Types - Floppy Disks (Diskettes) and Hard Disks
  • Hard disks
    • Non-removable
    • Inside your PC
    • Very fast
    • Hold large amounts of data
  • Diskettes
    • Removable
    • Hold up to 1.44 MB
    • Very slow
setting up a hard disk from scratch
Setting Up a Hard Disk From Scratch
  • Low level formatting
    • Hard disk supplied with low level formatting
    • DOS FORMAT command will not low level format a hard disk
  • Partitioning
    • With FDISK
  • High level formatting
    • Using DOS FORMAT command
disk partitions
Disk Partitions
  • Options include setting up:
    • A single primary partition
    • A single extended partition
    • Multiple logical drives
  • Manipulated via the DOS command FDISK
    • A logical drive is anything addressed by a drive letter
    • If you have a single large primary partition, it is referred to as drive C:
    • If you have an extended partition, use FDISK to split this into one or more logical drives
    • Referred to as drive D: E: F: etc.
high level logical formatting
High Level (Logical) Formatting
  • Also called logical formatting
  • All logical drives within hard disk partitions must first be formatted
  • Use the DOS FORMAT command
  • Only drive C: needs to be a system (bootable) disk
diskette formatting considerations
Diskette Formatting Considerations
  • System and non-system diskettes
  • Quick formatting


Non-System Disk!

unformatting a disk
Unformatting a Disk
  • When you format a disk, by default it saves information concerning the disks contents
  • Providing that you use the UNFORMAT command immediately this information can be used to restore the contents of the disk
copying and labelling diskettes
Copying and Labelling Diskettes
    • Uses identical source and target diskettes
speeding up disk access with defrag
Speeding Up Disk Access With DEFRAG
  • Removes file fragmentation
  • Speeds up disk access
  • Run DEFRAG if the disk appears slow

The effect can

sometimes be


  • Used to speed up access from the disk
  • Set up via the CONFIG.SYS
  • Setup via the AUTOEXEC.BAT
  • Can increase to AND from the hard disk
disk compression dblspace and drvspace
Disk Compression DBLSPACE and DRVSPACE
  • Compresses data held on a disk, and increases the storage capacity
  • Is it safe?
  • What about disk performance?



disk structures
Disk Structures
  • Sides
  • Sectors
  • Tracks
  • Clusters
the dos boot sequence
The DOS Boot Sequence
  • The boot record
  • Two hidden system files
ram disks
RAM Disks
  • You can treat part of your memory (RAM) as a virtual disk
  • Accessed much faster than a real disk
  • Useful with Windows, as you can create temporary files of a virtual disk (by pointing the TEMP= variable to the virtual disk, within the AUTOEXEC.BAT)
memory fundamentals

Memory Fundamentals

PC and DOS Essentials

type of memory chips ram and rom
Type of Memory Chips - RAM and ROM
  • RAM
    • Random Access Memory
    • Read/write memory
    • DOS and application programs are loaded into RAM
  • ROM
    • Read Only Memory
    • Contains hard coded information that is used by the operating system
    • ROM-BIOS
    • Video ROM
    • Hard disk ROM
the ibm pc the 8086 cpu and dos
The IBM PC, the 8086 CPU and DOS
  • The original IBM PC containing an Intel 8086 CPU and DOS were all released at the same time
  • The original PC was designed around the Intel 8086 CPU and DOS in turn was designed to run specifically on the 8086 CPU
  • DOS has since been left behind by the hardware, including the CPUs

It’s not 1981 anymore!


conventional memory
Conventional Memory
  • Defined by addressing limitations of the 8086/8088 CPU
  • Is the first 1 MB of memory
  • Not protected
  • Traditionally only 640 KB used by DOS and DOS applications
extended memory
Extended Memory
  • Protected Memory above 1 MB
    • Used by Windows and Windows applications
    • The original CPU for which DOS was designed only had 20 address lines, and could only address a maximum of 1 MB
    • In 1984, with the release of the IBM AT based on the Intel 80286 CPU, the number of address lines was raised to 24, giving a maximum memory address range of 16 MB
    • The first 1 MB was addressed in Real Mode, while the remaining 15 MB were addressed in Protected Mode and were referred to as Extended Memory
    • 386/486-based PCs can, in theory, address 4 GB of memory
  • Extended Memory Specification - (XMS)
    • Defines a standard used to access Extended Memory
    • DOS and Windows use a driver HIMEM.SYS to control access to the XMS memory
expanded memory an old technology
Expanded MemoryAn Old Technology!
  • Used only by certain DOS applications
    • Windows applications do not require Expanded Memory
    • Used to extend the life of old 8086-based PCs (which could only address 1 MB of Conventional Memory)
    • Modern DOS programs will tend to use Extended Memory rather than Expanded Memory
    • Traditionally requires a special Expanded Memory card and a special device driver
    • Requires a 64 KB page frame in the UMBs
  • May now be emulated from Extended Memory by using the EMM386.EXE device driver
the upper memory blocks and the high memory area

1 MB

640 KB

0 KB

The Upper Memory Blocks and the High Memory Area
  • The UMB space is located between 640 KB and 1 MB
  • The HMA is a 64 KB area just above 1 MB





using the umbs and hma devicehigh and loadhigh
Using the UMBs and HMA - Devicehigh and Loadhigh
  • Allows you to load items with the CONFIG.SYS and the AUTOEXEC.BAT above the 640 KB limit
    • DEVICEHIGH .....
    • LH .....
virtual memory used by windows
Virtual Memory - Used by Windows!
  • Treats part of your disk as if it were memory
    • Used by Windows and Windows applications, but not by DOS
    • Transparent to Windows applications
    • Only used when physical memory is full
    • DOS was designed for the Intel 8086 CPU, which did not support Virtual Memory. Consequently, DOS does not support Virtual Memory
    • Virtual Memory is used by Windows 3.1 which was designed to run on 286 and 386 CPUs (which do support Virtual Memory)
examining memory
Examining Memory
  • Use the MEM or MSD commands
  • System Info is available via the Help drop-down menu of most modern Microsoft applications
configuring your pc

Configuring Your PC

PC and DOS Essentials

the dos boot sequence54
The DOS Boot Sequence
  • ROM-based diagnostics run first
  • Then the Boot Record is executed
  • IO.SYS loads
  • MS-DOS.SYS loads
  • If a CONFIG.SYS is present, this is then loaded
  • COMMAND.COM is then loaded
  • Lastly, if present, the AUTOEXEC.BAT is loaded
conditional booting
Conditional Booting
  • To completely by-pass the DOS configuration
  • First either boot or re-boot the computer
  • When you see the message ‘Starting MS-DOS’ ...
    • Either depress (and release) the F5 key
    • or depress (and keep depressed) the Shift key
the config sys
  • The CONFIG.SYS file is optional and is used to customize the way your PC will work
    • For instance, it may be used to set up the country characteristics for countries other than the United States (DOS is basically American and needs customization for proper use outside the USA)
  • Device drivers are software that extend the function of DOS in a particular way
    • For instance, if you have installed a particular tape drive, you may need to install a tape device driver (supplied by the tape manufacturer) that instructs DOS on how to talk to the tape drive unit
the autoexec bat
  • A batch file that executes automatically when you boot the PC
  • Sets items such as the PROMPT and PATH
  • PROMPT $p$g
  • SET TEMP=C:\temp
the dos path
  • The PATH command is normally set from within the AUTOEXEC.BAT
  • Defines a search path for executable files or batch files (i.e. files that run when you type in the correct file name and press the Return key)
    • It is important to remember that by default DOS always searches the current directory first (i.e. the directory you are in when you issue a command)
    • The root directory of a disk will only be searched if it is the current directory, or if it is specified in the PATH statement
    • Held as an environment variable, within the DOS environment
      • A small area of memory used for storing variables for use by DOS, Windows or other applications
the dos environment
The DOS Environment
  • The DOS Environment is a small area of memory used by DOS, Windows and some other applications to store used items of information
  • Standard items include the Path, Prompt and COMSPEC variables
  • Windows uses the TEMP= variable to determine where to store temporary files
  • Use the SET command to view the contents of the Environment
loading high
‘Loading High’
  • Since the release of DOS 5 elements of DOS may be loaded above 640 KB
    • Use the DEVICEHIGH statement
    • Use the LH statement
  • Allows you to free up Conventional Memory for use by DOS application programs
configuring a windows based pc
Configuring a Windows-Based PC
  • Most Windows configuration is set via the Control Panel
what are batch files
What are Batch Files?
  • Batch files allow you to assign repetitive tasks to a small file which once created may be run as often as you wish
  • Batch files have a .BAT file extension
  • The AUTOEXEC.BAT is a batch file with the special property that it will run automatically each time you boot DOS
rem and echo
  • REM
    • This allows you to document a batch file
    • Not displayed on the screen

REM message

  • ECHO
    • May be used to turn off echoing of batch file statements


    • ECHO OFF often preceded by @, which turns echoing off for the line containing it


    • May be used to display (echo) messages to the screen

ECHO message

    • May be used in batch files to activate the system bleep


goto and call
  • GOTO
    • Allows you to go from one line to another, within the same batch file
    • A single trip (no automatic return)
    • You go to a label which is indicated by a preceeding colon (:)
      • :START
      • PAUSE
      • GOTO START
  • CALL
    • Used to transfer control from one batch file to another batch file
    • When the second batch file has finished processing, control automatically returns to the original batch file
  • Used to temporarily suspend batch file processing
  • By default displays a message

‘Press any key to continue’

i o device names and redirection
I/O, Device Names and Redirection
  • Standard devices include:
    • The console
    • The serial port
    • The parallel port
    • The console
    • The NUL device
  • Standard Output
    • Informational output that is displayed on the console (screen) by default
    • May be re-directed to the NUL device
  • Standard Error
    • Information concerning errors that is displayed on the console
    • Cannot be re-directed to the NUL device



  • The output of one command is fed directly into a second command, and will modify the output, which is then displayed on the standard device (i.e. the screen)
  • Used by certain DOS commands
    • MORE
    • FIND


The output is modified so that it is displayed one screen at a time

advanced batch file concepts

Advanced Batch File Concepts

PC and DOS Essentials

what are variables
What are Variables?
  • A variable is like a container such as a cup
    • The cup is always called a cup, but the contents of the cup can change
    • For instance the cup may contain coffee or tea
    • But the container is still called CUP
    • DOS can use this idea of a named container, i.e. variable
  • The DOS path is held in a container called PATH, it is always called Path, but as we know the contents of the Path may be changed





command line parameter substitution
Command Line Parameter Substitution
  • This concept allows you to run the batch file and specify parameters that are picked up by the batch file and used within it
    • Each parameter is separated by a space

BATCH_FILE Parameter1 Parameter2 Parameter3 ...

environment variable substitution
Environment Variable Substitution
  • The DOS environment is a small area of memory used for storing variables
  • Environment variables include:
  • To set an Environment variable use the syntax:
    • SET variable= value
  • To put an Environment variable into a batch file use:
    • %enviroment_variable_name%
  • To add an Environment variable to the DOS path, use:
    • PATH=%PATH%;%1
    • NB: This assumes that the existing path does not end with a semi-colon (;)
if exist
  • Used to detect the existence of a particular file
  • NOTE that this command will NOT detect the existence of a directory



if errorlevel
  • ERRORLEVEL is supported by:
    • XCOPY
  • Some DOS commands issue ERRORLEVEL reports on completion
  • Also called return codes or exit codes
    • An Error level of 0 normally indicates success
    • An Error level above 1 normally indicates failure





doskey macros
  • Use DOSKEY to create them
  • Similar to DOS-based batch files BUT held in memory, not on the disk
  • Faster than Batch files
  • Volatile
  • Load via the AUTOEXEC.BAT if you want to make them more permanent


PC and DOS Essentials

types of laser printer pcl vs postscript
Types of Laser PrinterPCL vs Postscript
  • PCL (Printer Control Language)
    • Not so good for DTP
    • Device dependent
    • Reasonably fast
    • PCL5 used in HP LaserJet 4 series
    • Normally used with resolution enhancement
  • Postscript
    • Much more flexible and configurable
    • Slower
    • More expensive hardware required
    • Ideal for graphics and DTP
    • Device resolution dependent
printer considerations
Printer Considerations
  • Important items to consider when specifying a printer are:
    • Speed
    • Resolution
    • Resolution Image Enhancement
    • Printer memory
    • Duplex printing
printer drivers for dos and windows
Printer Drivers for DOS and Windows
  • Each DOS program requires its own printer driver
  • All Windows programs use a single Windows printer driver


security backups and viruses

Security, Backups and Viruses

PC and DOS Essentials

what are viruses

Suddenly, I do

not feel so well!

What are Viruses?
  • Viruses can cause permanent loss of data
  • Viruses spread from one PC to another, even across networks
  • ALWAYS use a virus checker on your disks
virus protection methods dos and windows
Virus Protection Methods DOS and Windows
  • MSAV
    • Run from the command line or from the AUTOEXEC.BAT
    • TSR program
    • Constantly on alert for viruses
  • Windows 3.1 is given anti-virus tools by DOS
  • Under DOS
    • Use MSBACKUP
  • In Windows
    • Open the File Manager and click on the Backup command, located under the Tools drop down menu

Perform REGULAR backups!

fixing errors on a disk
Fixing Errors On a Disk
  • Disks are physical devices, and disk drives are full of moving parts
  • Like anything else, they are prone to wear and tear as they get older
  • CHKDSK /F and SCANDISK can be used to fix a range of problems that may occur on your disks

Use SCANDISK rather than CHKDSK it is safer and more effective

windows fundamentals

Windows Fundamentals

PC and DOS Essentials

the advantages of using windows
The Advantages of Using Windows
  • The Microsoft sales pitch
    • Multitasking
    • Uses all available memory
    • Has a consistent User Interface
    • Allows programs to talk to each other
  • The down side
    • Prone to crashing
    • Does not multitask in a sensible way
select then manipulate
Select, then Manipulate!
  • The basic rule when using Windows!
components of a window
Components of a Window
  • The Title Bar
  • The Menu Bar
  • Borders
maximizing minimizing and restoring a window
Maximizing, Minimizing and Restoring a Window
  • Maximize
    • Causes the program to fill the whole screen
  • Minimize
    • Causes the program to be displayed as an icon
  • Restore
    • Restores an icon to a window, or a full screen program to a window
moving and re sizing a window
Moving and Re-sizing a Window
  • Any program displayed as a window within Microsoft Windows can be moved around on the screen
  • Any program displayed as a window within Microsoft Windows can be re-sized either horizontally, vertically, or in two dimensions at the same time
menus and dialog boxes
Menus and Dialog Boxes
  • All windows programs have drop down menus of one sort or another. The drop down menus within a Windows program allow you to interact with a program. For instance, most applications have a File drop down menu containing commands such as Open, Save, or Exit
multitasking within windows
Multitasking Within Windows
  • When you multitask programs under Windows on your PC, they appear to run simultaneously
    • In fact each program is allocated a small proportion of the CPUs attention and whilst one program is running, the other programs are temporarily suspended
    • By default, all Windows applications will appear to run simultaneously, whilst DOS programs will only run when in the foreground
using the task list
Using the Task List
  • Displayed in a window and, as the name suggests, lists all the tasks (i.e. programs) that are currently running in memory
  • Allows you to easily switch to any of the programs listed in it, or to close any program listed in it
  • Can tile or cascade programs
    • This causes each separate program that is running to be displayed either side-by-side, or in a layered fashion
  • You can arrange the icons at the bottom of the screen
program manager groups
Program Manager Groups
  • A number of standard groups are installed by default
    • Main group
    • Accessories group
    • Games group
    • StartUp group
  • Groups can be added, deleted or modified
manipulating groups and adding programs
Manipulating Groups and Adding Programs
  • Click on File and select New

This dialog box is displayed when you create a new program group or program item

file manager terminology
File Manager Terminology
  • It is important to understand the terminology associated with using the File Manager
directories and drives
Directories and Drives
  • Make sure that you know how:
    • To expand a directory level
    • To expand all directory levels
    • To indicate expandable branches
    • To collapse a directory level
    • To display a particular directory
    • To change the active disk drive
the control panel
The Control Panel
  • Allows you configure items including:
    • Colors and Fonts
    • Ports
    • Mouse and Keyboard
    • Desktop
    • Printers
    • International settings
    • Date/Time
    • Sound and Drivers
    • 386 Enhanced