Introduction to
Information Technology
LECTURE 11: INTRODUCTION TO COMPUTER
ARCHITECTURE AND SOFTWARE
IT 101 Section 3
Department of Electrical and Computer Engineering
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Introduction to Computer Architecture
GOALS
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Knowledge of some computer history milestones
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Basic understanding of computer hardware and software
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Understanding of basic hardware elements in a desktop computer:
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Understanding of the hierarchy of computer software
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IBM PC
1981
CPU
Memory
Storage
Input/Output
Applications
Computer languages
Operating systems
Assembly code and machine language
Apple Mac
1984
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Calculating Machines Through History
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The Abacus
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5000 years old
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Addition and subtraction
Mechanical Calculators
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Charles Babbage’s
mechanical calculators
prefigured modern
computers
Electronic “Calculators”
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Vacuum Tubes
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Transistors
Modern Computer
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Microprocessors
Charles Babbage’s
Difference Machine
(Picture courtesy of Science
Museum/Science & Society
Picture Library)
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ENIAC
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What were computers like just over 50 years ago?
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1946 - ENIAC
Used plugboards and switches to program
Used vacuum tubes
Developed at UPenn
Funded by U.S. government
Electronic Numerical Integrator and Computer
ENIAC
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Computer Generations
Ultra Large Scale Integration
> 100 million devices per chip
Very Large Scale Integration: Post 1978
100,000 - 100 million devices per chip
Vacuum Tubes
1946-1957
Transistors
1958-1964
Large Scale Integration: 1971-77
3000- 100,000 devices per chip
Medium Scale Integration: Pre-1971
100-3000 devices per chip
Small Scale Integration: 1960s
Up to 100 devices per chip
INTEGRATED CIRCUIT
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Moore’s Law
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Intel pioneer, Gordon Moore, predicted in 1965 that the number of
transistors on a chip would double every 18 months.
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Some Computer Hardware
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Inside the Computer
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CPU, Memory Chips
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Floppy drive, Hard disk, CD-ROM,
DVD Player
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Motherboard, Expansion Slots,
Power Supply
Back of Computer
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Cooling Fan, Power Connector
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Keyboard and Mouse Connectors
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Parallel Printer Port
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Video Connector
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Desktop Computer Hardware
From the optional textbook, The Digital Information Age
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Four main functional units of a computer
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Central Processing Unit (CPU)
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Memory
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Storage
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Input/Output
Storage
Input/Output
Central Processing
Unit
Memory
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Central Processing Unit - CPU
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The Microprocessor
The brains, or main processing unit, of the computer
Performs calculations and completes instructions
Performance based on clock speed
Pentium 4 -- 2.8 GHz chip operates at 2.8 billion cycles per
second
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Four Stages of CPU Operation
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Fetch - Seeks instructions from outside source
Decode - Analyzes the instructions to determine which of the chip’s
circuits should be used for processing
Execute - Performs the actual instructions
Store - Places processing result in appropriate place
Comparing a Dime to a Microprocessor
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The CPU
Storage
Control
Unit
Arithmetic
Logical
Unit
(ALU)
Registers
Input/Output
Flags
Cache
Memory
Memory
Execution of
instructions
occurs here.
Grouping of
transistors
(logic gates)
that perform
logical and
mathematical
functions
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Memory
Computers require storage in order to process information.
TWO TYPES OF COMPUTER MEMORY
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Temporary
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Long-Term
RAM – Random Access Memory
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Can read or write data
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E.g. cache memory (on the CPU)
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Measured in MegaBytes (MB)
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Volatile memory: erased when computer powered off
ROM – Read only memory
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Permanently stored information used repeatedly by
computer
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Can never accept new information
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Normally installed by system manufacturer
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Non-volatile
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Storage
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Provides long-term retention of data on magnetic or optical disk
Hard Drive
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Disc capacity currently measured in GigaBytes (GB)
Floppy Disc
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Typical capacity of 1.44 MegaBytes (MB)
Compact Disc
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650 MB
Zip Drive
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Removable floppy discs that store up to 250 MB
DVD
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Optical storage
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Input/Output devices
Moves data between the computer and its external environment.
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Input Devices - Accepts data from external sources and converts to
electric signal
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Keyboard, Mouse, Touch screen, Voice activation, Video Camera,
Microphone, Scanner, JoyStick
Output Devices - Accepts electric signals from CPU and converts them to
an output device.
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Monitor
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Printer
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Speakers
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Communication ports
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Input/Output
Game Board
Graphics Board
CPU
Serial Port
Parallel Port
Serial Port
Network Port

Sound Board
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Monitor
Mode
Local Area Network

ADC
bus
input/output
Analog signal source
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Applications
Computer Software
Programming Language
(High Level Language)
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Software consists of instructions and
application programs that permit
computers to accomplish tasks.
It is called software because, unlike
hardware that has fixed configurations,
connections, and operation, software is
flexible and easily modified.
Operating System
Assembly Code
Machine Language
Hierarchy of Software
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Machine Language
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01100100100101010
Lowest level language
Consists of elementary
instructions directly recognized
by the CPU
Provides numerical codes
directly recognized by the CPU
Machine language programming
produces a string of numbers
Not commonly used anymore
Application
Programming Language
(High Level Language)
Operating System
Assembly Code
Machine Language
How does it relate to “Assembly Language?”
Hierarchy of Software
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Assembly Code
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Also called Assembly Language
Also consists of elementary
instructions directly recognized
by the CPU, but uses codes
rather than numbers.
Assembly code is different for
every type of computer.
(i.e. it is CPU specific)
Cumbersome to develop.
Difficult to later read and modify
An “assembler” converts
assembly language to machine
language.
Application
Programming Language
(High Level Language)
Operating System
Assembly Code
Machine Language
Hierarchy of Software
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Operating System
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Computer program that links
various hardware components
to one another
Stored on hard disk
Loaded to memory when the
computer is turned on
Once in memory, the
operating system takes over
and manages the system
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Provides a user interface
Manages memory
Controls directory access
Supports hardware
Supports applications
Examples of O/S?
Application
Programming Language
(High Level Language)
Operating System
Assembly Code
Machine Language
Hierarchy of Software19
Examples of Operating Systems
MS-DOS
Introduced in 1981
Microsoft’s first O/S
Microsoft Disk Operating
System (MS-DOS)
Text based O/S -- C:/>
Mac OS
Appeared in 1984
Apple Macintosh
Icons and Graphical User
Interface (GUI)
Microsoft Windows
Dominates PC market
Windows 3.x in 1990
Windows 95 and 98
Windows NT
Windows 2000
Windows XP
IBM OS/2
Roughly 1992
Split with Microsoft
Never took off
Unix Variations
IBM’s AIX
Hewlett Packard’s HP/UX
Sun’s Solaris
Linux
Others
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The Linux Operating System
What’s different about Linux?
Why do we hear so much about this?
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Linus Torvalds developed Linux in 1991.
Linux’s open source code is freely available on the web.
Most software is in a compiled, computer-readable, ready-to-run
format that conceals how the software was developed.
Open source code is source code that anyone can view/modify.
Linux is a competitor to Windows NT/2000, especially in the
business “server space.”
Other software based on open source code includes the Apache web
server and PERL, a web scripting language.
What are the advantages and disadvantages of open source code?
Key Concept: Open Source Code
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Programming Languages
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Application
A computer program tells a
computer what to do.
Programming Language
(High Level Language)
Needs to be written in a
programming language the
computer can understand.
Operating System
A “compiler” translates almost
human syntax into lower level code
the computer can “execute.”
Assembly Code
Theoretically no longer CPU-specific
like assembly code.
What are some examples of
programming languages?
Machine Language
Hierarchy of Software
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Programming Language Evolution
FORTRAN
(Formula Translator)
Developed by IBM
Science/engineering
1957
Basic
(Dartmouth College,
Kemeny and Kurz)
Simple language
students could learn
1964
COBOL
(Common Business
Oriented Language)
Pushed by U.S. Govt.
1960
Pascal
Once popular with
serious
programmers
1970s
Installed base of
code in COBOL still
considerable
Appeal has
diminished
C and C++
Developed originally
as C/Unix in
1974
C++ is object
oriented version
HTML
HyperText Markup
Language
describes documents
on the Web
Visual Basic
Microsoft’s “visual
language”
Provides an array of
tools that decrease
development time
Java
Developed by Sun
O/S independent
XML
eXtensible Markup
Language
More powerful
successor to HTML
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Key Programming Terms
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Programming is telling the computer what to do.
Source Code is a series of commands written in a programming
language.
Programming languages are sometimes divided into 4
categories:
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1GL (first generation language) - Machine language
2GL (second generation language) - Assembly language
3GL (third generation languages) - Cobol, Pascal, C, Basic
4GL (fourth generation languages) - vague, diverse term that
includes object oriented programming languages, visual languages,
and markup languages.
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Application Software
“Shrink-wrapped software”
available at the store
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Program at the command of the user.
Application programs can be downloaded
from web sites or installed from a CD-ROM.
They install almost automatically.
Microsoft Office
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MS Word – word processing
MS Excel – spreadsheet program
MS PowerPoint – presentations
MS Access 2000 – DBMS (database
management system)
AOL Instant Messenger
Voice Recognition Software
Oracle DBMS
Netscape Navigator
Application
Programming Language
(High Level Language)
Operating System
Assembly Code
Machine Language
Hierarchy of Software
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Recommended Optional Excursion
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“Information Age” Exhibit at The Smithsonian’s American History
Museum
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Chronicles the birth and evolution of information technology
Contains many famous information technology artifacts:
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Samuel Morse’s telegraphs
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Alexander Bell’s telephones
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A Hollerith punched card machine
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The ENIAC computer
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Early personal computers
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Introduction to Information Technology