Transcript Introduction to Computers

Introduction to Computers
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Chapter Goals
• Describe the history of computer hardware
and software
• Describe the changing role of the computer
user
• Distinguish between systems programmers
and applications programmers
• Distinguish between computing as a tool and
computing as a discipline
• List the basic components of a computer
system
• Understand what a Computer Program is
• List the Programming Life-Cycle Phases
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Computing Systems
Hardware The physical elements of a
computing system (printer, circuit boards,
wires, keyboard…)
Software The programs that provide the
instructions for a computer to execute
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Early History of Computing
Abacus
An early device to record
numeric values
Blaise Pascal
Mechanical device to add,
subtract, divide & multiply
Joseph Jacquard
Jacquard’s Loom, the punched
card
Charles Babbage
Analytical Engine
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Early History of Computing
Ada Lovelace
First Programmer
Alan Turing
Turing Machine, Artificial Intelligence Testing
Harvard Mark I, ENIAC, UNIVAC I
Early computers launch new era in mathematics, physics,
engineering and economics
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First Generation Hardware
(1951-1959)
Vacuum Tubes
Large, not very reliable, generated a lot of heat
Magnetic Drum
Memory device that rotated under a read/write head
Card Readers  Magnetic Tape Drives
Sequential auxiliary storage devices
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Second Generation Hardware
(1959-1965)
Transistor
Replaced vacuum tube, fast, small, durable, cheap
Magnetic Cores
Replaced magnetic drums, information available
instantly
Magnetic Disks
Replaced magnetic tape, data can be accessed directly
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Third Generation Hardware (19651971)
Integrated Circuits
Replaced circuit boards, smaller, cheaper, faster, more
reliable.
Transistors
Now used for memory construction
Terminal
An input/output device with a keyboard and screen
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Fourth Generation Hardware
(1971-?)
Large-scale Integration
Great advances in chip technology
PCs, the Commercial Market, Workstations
Personal Computers were developed as new companies
like Apple and Atari came into being. Workstations
emerged.
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Parallel Computing and
Networking
Parallel Computing
Computers rely on interconnected central processing
units that increase processing speed.
Networking
ARPANET and LANs  Internet
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First Generation Software (19511959)
Machine Language
Computer programs were written in binary (1s and 0s)
Assembly Languages and translators
Programs were written in artificial programming
languages and were then translated into machine
language
Programmer Changes
Programmers divide into application programmers and
systems programmers
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Second Generation Software
(1959-1965)
High Level Languages
Use English-like statements and make programming
easier.
Fortran, COBOL, Lisp are examples.
High-Level
Languages
Assembly
Language
Machine
Languag
e
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Third Generation Software (19651971)
• Systems Software
– utility programs,
– language translators,
– and the operating system, which decides which
programs to run and when.
• Separation between Users and Hardware
Computer programmers began to write
programs to be used by people who did not
know how to program
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Third Generation Software (19651971)
Application Package
Systems Software
High-Level Languages
Assembly Language
Machine Language
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Fourth Generation Software (19711989)
Structured Programming
Pascal, C, C++
New Application Software for Users
Spreadsheets, word processors, database management
systems
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Fifth Generation Software (1990present)
Microsoft
The Windows operating system, and other Microsoft
application programs dominate the market
Object-Oriented Design
Based on a hierarchy of data objects (i.e. Java)
World Wide Web
Allows easy global communication through the Internet
New Users
Today’s user needs no computer knowledge
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Computing as a Tool
Programmer / User
Systems Programmer
(builds tools)
Applications Programmer
(uses tools)
Domain-Specific Programs
User with No
Computer Background
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Computing as a Discipline
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What can be (efficiently) automated?
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Four Necessary Skills
1.
2.
3.
4.
Algorithmic Thinking
Representation
Programming
Design
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Computing as a Discipline
What do you think?
Is Computer Science a mathematical,
scientific, or engineering discipline?
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Systems Areas of Computer
Science
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Algorithms and Data Structures
Programming Languages
Architecture
Operating Systems
Software Methodology and Engineering
Human-Computer Communication
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Application Areas of Computer
Science
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Numerical and Symbolic Computation
Databases and Information Retrieval
Artificial Intelligence and Robotics
Graphics
Organizational Informatics
Bioinformatics
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Computer Components-Hardware
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Memory Unit
•
is an ordered sequence of storage cells,
each capable of holding a piece of
information
•
each cell has its own unique address
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the information held can be input data,
computed values, or your program
instructions.
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Memory Unit
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RAM and ROM
• RAM stands for Random Access Memory
– Inherent in the idea of being able to access each
location is the ability to change the contents of each
location
• ROM stands for Read Only Memory
– The contents in locations in ROM cannot be changed
• RAM is volatile, ROM is not
– This means that RAM does not retain its bit
configuration when the power is turned off,
but ROM does
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Secondary Storage Devices
• Because most of main memory is volatile
and limited, it is essential that there be
other types of storage devices where
programs and data can be stored when
they are no longer being processed
• Secondary storage devices can be
installed within the computer box at the
factory or added later as needed
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Magnetic Tape
• The first truly mass
auxiliary storage
device was the
magnetic tape drive
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Magnetic Disks
• A read/write head travels across a spinning
magnetic disk, retrieving or recording data
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Compact Disks
• A CD drive uses a
laser to read
information stored
optically on a plastic
disk
• CD-ROM is ReadOnly Memory
• DVD stands for
Digital Versatile Disk
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Peripherals
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are input, output, or auxiliary storage devices
attached to a computer
–
Input Devices include keyboard and mouse.
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Output Devices include printers, video display,
LCD screens.
–
Auxiliary/Secondary Storage Devices include
disk drives, scanners, CD-ROM and DVD-ROM
drives, modems, sound cards, speakers, and
digital cameras.
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Central Processing Unit
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has 2 components to execute program
instructions
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Arithmetic/Logic Unit performs arithmetic
operations, and makes logical comparisons.
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Control Unit controls the order in which
your program instructions are executed.
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Flow of Information
• The parts are connected to one another by a
collection of wires called a bus
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The Fetch-Execute Cycle
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Fetch the next instruction
Decode the instruction
Get data if needed
Execute the instruction
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The Fetch-Execute Cycle
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