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2
What is a computer?
• A computer is a electromechanical device which can be
programmed to change (process) information from one
form to another.
– Do exactly as they are told.
– Digital devices: Understand only two different states
(OFF and ON)

3
Traditional Types of Computers
• General purpose computers
–Mainframe
–Minicomputer
–Microcomputer (Personal Computer)

4
• First computers, introduced in 1950s
• Used by large businesses
• Typically supported 100 to 500 users
• Very expensive
• Used for very large processing tasks
• Mainframe
Computers

5
• Typically supported 10 to 100 users
• Smaller and less expensive than mainframes
• The real difference is relative in terms of price, power,
marketing.
• Minicomputers

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• Small, self-contained computers
with their own CPUs
• Used by home and business
users
• Uses a microprocessor, a CPU
(Central Processing Unit) on a
single chip.
• Microcomputers
(Personal
Computer or PC)

7
Portable Computer
• Desktop computers
• Laptop computers
• Personal Digital Assistants (PDAs)
• What are these types of
portable computers (a type
of personal computer)?

8
Networked computer
• Networked computer = Computers connected to other computers or
peripheral devices (printers, etc.) to share information.
• What is the difference between these two networked devices?
Intelligent terminal (computer) Dumb terminal
• No CPU (uses server’s)
• No Operating system (uses
server’s)
• Input and Output only

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Embedded Computers
• Embedded computers – Computers found in consumer
goods in order to enhance their function.

10
Special Purpose Computers
• Special purpose or dedicated computers – A device with a
specific purpose such as game system or information
kiosk.

11
Hardware versus Software
• Hardware = The
physical components
that make up a
computer system.
– More in a
moment…
• Much more on all of
these items in later
presentations!

12
Hardware versus Software
• Software = The
programs (instructions)
that tell the computer
what to do.
– System Software
– Application Software
– Stored on a storage
media such as hard
disk, CD-ROM, floppy
disk, tape, etc.
– More later…

13
Hardware Components
• This is just an overview, more later…

14
Hardware Components
SYSTEM UNIT
INPUT OUTPUT
PERMANENT
STORAGE
Know these!

15
The Processor
Let’s open the box!

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The Processor
circuit board = a board with
integrated circuits
(microchips)
• system board or
motherboard
• interface boards or expansion
boards
system board or motherboard
= a single circuit board with
the components which make
up the computer’s processor
for a microcomputer, including
the:
• CPU (Central Processing
Unit)
• Memory
– RAM
– ROM or ROM BIOS
• expansion slots

17
The Processor: The CPU
CPU (Central Processing Unit) = A complex collection of electronic
circuits on one or more integrated circuits (chips) which:
1. executes the instructions in a software program
2. communicates with other parts of the computer system, especially
RAM and input devices
The CPU is the computer!

18
Input and Output Devices
SYSTEM UNIT
INPUT OUTPUT
PERMANENT
STORAGE

19
Input Devices
• Enter information
into a computer
• Examples:
– Mouse
– Keyboard
– Trackball
– Touchpad
– Light pen
– Joystick
– Digital camera
– Microphone
– Bar code reader
– Scanner

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Output Devices
• Send information out from a PC
• Examples:
– Speakers
– Monitors
• Visual Display Unit (VDU), Cathode Ray Tube (CRT),
Liquid Crystal Display (LCD), Light-Emitting Diode
(LED)
– Printers

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System Unit - Revisited
SYSTEM UNIT
INPUT OUTPUT
PERMANENT
STORAGE
System Unit:
• CPU (Central Processing Unit)
• Memory
– RAM
– ROM or ROM BIOS
• expansion slots

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RAM (Random Access Memory)
RAM (Random Access Memory) = integrated circuits (chips) used to
temporarily store software (programs, instructions) and data
• “primary” storage for the CPU
• electronic switches, storing ON’s and OFF’s
Temporarily stores for the CPU:
• Software
– operating system software
– application software
• Data
– data (documents, spreadsheets, etc.)

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Inserting RAM
RAM is TEMPORARY memory
RAM is volatile
• stores ON and OFF bits (software and data) electrically
• when power goes off, everything in RAM is lost

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RAM: Speed
Why does the CPU use RAM?
• The CPU is very FAST!
• The CPU needs the instructions (software) and data as quickly as
possible
• If the CPU has to wait, so does the user
Why doesn’t the CPU use permanent storage like disk drives?
• Too slow

25
RAM: Capacity
The amount of RAM determines:
• what software and data the user can work on
• how much software and data the user can work with
• Most computers have at least 256 MB (Megabytes, 256 million bytes)
“out of memory” error message from the Operating System
The more complex and sophisticated the software, the more instructions
that software contains, which means larger software files.

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ROM (Read Only Memory)
ROM (Read Only Memory) = integrated circuits (microchips) that are used
to permanently store start-up (boot) instructions and other critical
information
Read Only = information which:
• Cannot be changed
• Cannot be removed
• Cannot be appended (added to)
• Fixed by manufacturer

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ROM (Read Only Memory)
ROM is sometimes known as ROM BIOS (Basic Input Output System
software)
ROM permanently contains:
• start-up (boot) instructions
• instructions to do “low level” processing of input and output devices,
such as the communications with the keyboard and the monitor
Firmware = software program which is stored permanently on a
microchip, such as the software on the ROM chip

29
Storage Devices
SYSTEM UNIT
INPUT OUTPUT
PERMANENT
STORAGE
• Storage Devices:
– Floppy disks
– CD-ROMs
– Hard disks
– Zip disks
– Tape drives

30
Floppy disks
• Store up to 1.44 MB of data
• Usually 3.5" square disks
• Removable
Write-Protect tab
(Open means “write
enabled”)

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Hard disks
• Fixed permanently in a hard disk
drive inside a system unit
• Used to store the operating
system, applications, and data
• Can not buy more expansion
(easily)

32
CD-ROMs
• Read-only memory devices
(but CD-R and CD-RW
discs are recordable)
• Store up to 650 MB of data
• Portable and can be used
on any computer that has a
CD-ROM drive
• CD-R (CD Recordable)
• CD-RW (CD Rewritable)

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Flash sticks or memory
• Storage
• Digital Player
• Voice Recorder

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Zip disks
• Store up to 250 MB of data
• Used for backing up files or
transporting large files

35
Tape drives
• Work like a tape recorder
• Vary in capacity and
access speed
• Relatively expensive
• Generally used to back up
data
• Good for “archiving”
information
• Types
– Cartridge (slowest)
– DAT (Digital Audio
Tape)

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Computer Performance
• CPU speed (and type)
• Amount of RAM (and
speed)
• Hard disk capacity

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Computer Performance
• CPU Speed
– Governed by a clock
– Measured in millions of
cycles per second, or
megahertz (MHz)
• 700 MHz means 700
million operations per
second
– Measured in billions of
cycles per second, or
megahertz (GHz)
• 1.133 MHz means 1
billion, 133 million
operations per second

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Software
• System Software
• Application Software

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Application Software
• Performs specific tasks:
– Word processing
– Calculations
– Information storage and
retrieval
– Accounting
• Cannot function without the
OS (Operating System)
• Written for a specific
operating system and
computer hardware.

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Operating System Software
• Loads automatically when
you switch on a computer
• Main roles:
– Controls hardware and
software
– Permits you to manage
files
– Acts as intermediary
between user and
applications

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Software which manages the overall operation of the
computer system including:
• hardware (CPU, RAM, I/O)
• security
• system interface
• application interface

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GUI – Graphical User Interface
Windows 3.1
Windows
95/98/XP

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GUI – Graphical User Interface
MAC OS
UNIX/LINUX with
X-Windows

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CLI – Command Line Interface
• No GUI
• MS DOS
• ? Windows 97 ?

45
RAM
0
256
MB
Hard Disk Drive
CPU
ROM
Application Software
User data (information)
“The kernel”
MS Word

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1-ComputerBasics.ppt

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