Introduction to Computers,
Problem Solving, and
Programming
Chapter 1
1.1 Overview of Computers
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Computer - “A device for counting or computing”
Dr. John Atanasoff - 1st computer (1930).
ENIAC 1946 at U of Penn (30 Tons, 30-by-50 foot space,
data in memory, programmed by connecting switches and
wires)
Dr. John Von Neumann - Princeton
– Stored program concept
– Memory rather than wires and switches.
Evolution
– 1970s: Apple microcomputers
– Minicomputers
– Mainframes (time-sharing systems)
– Supercomputers: for very computing-intensive tasks
– Personal computers/Workstations
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– Laptops
Overview of Computers
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Von Neumann architecture basis for today's
computers
VLSI Technology made computers
affordable, small and available to the public
How programming has changed over time
3
1.2 Computer Hardware
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Every computer is organized roughly into
six parts
– CPU - central processing unit
• Where decisions are made, computations are
performed, and input/output requests are delegated
– Main Memory
• Stores information being processed by the CPU
– Secondary Memory
• Stores data and programs
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Computer Hardware
– Input devices
• Allows people to supply information to computers
– Output devices
• Allows people to receive information from
computers
– Network connection
• Modems / Ethernet interface
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Computer Components
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Main Memory
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Address
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Contents
0
1
1024
-27.2
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354
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.005
75.62
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Main Memory
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Stores
– programs
– data
– results
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Types
– RAM
– ROM
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Secondary Memory & Storage
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Semi permanent data-storage capability
– Tape or Disk
– Hard disk
– CD ROM
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Secondary memory has much more storage
capacity
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CPU
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“Brains” of the computer
– Arithmetic calculations are performed using the
Arithmetic/Logical Unit or ALU
– Control unit decodes and executes instructions
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Arithmetic operations are performed using
binary number system
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CPU
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Fundamental building block is a switch
– Switches are made from ultrasmall transistors
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Examples
– The Pentium ® processor contains about three
million transistors
– The Pentium Pro ® has about 5.5 million
transistors
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Input / Output Devices
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Accessories that allow computer to perform
specific tasks
– Receiving information for processing
– Return the results of processing
– Store information
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Common input and output devices
– Printer
– Keyboard
Joystick
Monitor
CD-ROM
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Computer Networks
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LAN - Local area network
– Organizational
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WAN - Wide area network
– Internet
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World Wide Web
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Introduced 1989
Developed by CERN
– European Laboratory for Particle Physics
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Web browser
– GUI
– Netscape
– IE
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1.3 Computer Software
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Application software
– Programs designed to perform specific tasks
that are transparent to the user
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System software
– Programs that support the execution and
development of other programs
– Two major types
• Operating systems
• Translation systems
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Application Software
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Application software is the software that
has made using computers indispensable
and popular
Common application software
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–
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Word processors
Desktop publishing programs
Spreadsheets
Presentation managers
Drawing programs
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Operating System
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Controls and manages the computing resources
Important services that an operating system provides
– File system
– Commands that allow for manipulation of the file
system
– Ability to perform input and output on a variety of
devices
– Management of the running systems
Examples
– MSDOS ®, Windows ®, Unix ®
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Programming Languages
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Machine Language
– “Native tongue” of the computer
– Binary 0s and 1s that specify what to do
• 0010 0000 0000 0100
• 1000 0000 0000 0101
• 0011 0000 0000 0110
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Assembly language
– Mnemonic code
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High - Level Languages
– Resemble human language (C++, C, Pascal)
• cost = price + tax;
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Programming Languages
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Language Standard
– Syntax (grammatical form) (=> rules)
– Portability
• programs ideally need no modification when moved
from one machine to another
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Source Program
Object Program
Executable Program
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Object Oriented Programming
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OOP derived from C
Bjarne Stroustrup (AT&T)
Since mid-1980s, standard 1998
Popular a.o. because of:
– Reuse of Classes and objects
– Efficiency
Class
– Definition of attributes and methods of an object
Method
– An operation that uses the object data
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OO Programming and
Structured Programming
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Object
– An instance of a class that has all the attributes and
methods included in the class definition
C++ is organized in a hierarchy
– Super Classes (“Father Classes”)
• It includes some of attributes and methods of a subclass
– Sub Classes (Son Classes)
• It is derived from a super class and it may contain own
attributes and methods
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Object-oriented design and programming supports good
software engineering
– Algorithms operate on well-defined data
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OO Programming and
Structured Programming
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Object-oriented design promotes thinking about software
in a way that models the real world
– Objects may model real things
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Algorithms are the basis for the procedural
sections (Structured Programs)
– Highly structured
– Top-down design
– Step-wise refinement
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Procedural languages (e.g. C, Pascal, Fortran):
– No clear relationship between algorithms and data
– OO tries to fill this gap
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Object Oriented Design
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Abstraction (Different views on the same object!)
– Extract the relevant properties of an object while
ignoring inessential details
– Ignore irrelevant properties
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Encapsulation (Access only through interfaces!)
– Breaking down an object into parts, hiding and
protecting its essential information, and supplying an
interface to modify the information in a controlled and
useful manner
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Object Oriented Design
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Modularity
– Dividing an object into smaller pieces or
modules such that the object is easier to
understand and manipulate
– E.g. “Consists–of” relationship!
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Hierarchy
– Ranking or ordering of objects based on some
relationship between them
– E.g. “Is-A” relationship!
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Abstraction
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Process of extracting only the relevant
properties of an object
Extracted properties define a view of the
object
Different contexts may have different views
or abstractions
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Abstraction
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Examples:
– Car dealer views a car from selling features
standpoint
• Price, warranty, color, etc.
– Mechanic views a car from systems
maintenance standpoint
• Oil, oil filter, spark plugs, etc.
– Abstraction depends on the context
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Encapsulation
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Breaking down an object into parts, hiding
and protecting its essential information, and
supplying an interface to modify the
information in a controlled and useful
manner
By hiding the information its representation
and content can be changed without
affecting other parts of the system
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Encapsulation
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Example - car radio
– Controlled by switches and buttons
– The details of how it works is hidden
– No manipulation of the car radio is allowed
except using the provided switches and buttons
–  Encapsulation restricts the use to interfaces
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Modularity
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Dividing an object so that the object holds
useful information and it is easier to
understand
Most complex systems are modular
– Cooling System
– Ignition System
– Fuel System
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Modularity
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Example - Automobile can be decomposed
into subsystems
– Cooling system
• Radiator
• Thermostat
• Water pump
– Ignition system
• Battery
• Starter
• Spark plugs
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Hierarchy
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Ranking or ordering of objects based on
some relationship between them
Hierarchies facilitate understanding
complex organizations and systems
– Example - a company hierarchy helps
employees understand the structure of their
company and their positions
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Hierarchy
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Example:
- Type
- # Wagons
Train
Means of
transportation
- # Doors
- Fuel type
VW
- Color
- Year
Car
BMW
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OO Classes
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Later we will use data abstractions
– C++ language
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Will apply OO techniques
– Structured Programming
– Object Oriented Programming
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Model our own objects or abstractions
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1.4 Processing a High-Level
Language Program
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Set of programs used to develop software
A key component is a translator
Types of translators
– Compiler
– Linker
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Examples
– g++, Borland C++ ®, Microsoft Visual C++ ®
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Processing a Program
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Editor used to enter the program
– Source program (file.cpp)
– UNIX vi text editor
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Compiler translates the source program
– Displays syntax errors (not descriptive)
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Linker/Loader to combine object file with
other object files
– Executable program
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Processing a Program
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Major activities
– Editing
– Compiling
– Linking with pre-compiled files
• Object files
• Library modules
– Loading and executing
– Viewing the behavior of the program
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Process Cycle
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1.5 Software Development
Method
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Steps for any Software development process
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1. Specify the problem requirement
2. Analyze the problem
3. Design an algorithm for solving the problem
4. Implement the algorithm
5. Test and verify the program
6. Maintain and update the program
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Software Development
Method
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Problem requirement
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What is the problem exactly?
Eliminate irrelevant aspects
Clear and unambiguous problem statement
Needs interaction with the person who posed the
problem
Problem Analysis - (Correct Problem)
– Identify data objects
– Determine Input / Output data
– Identify constraints on the problem/solution
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These two steps are very important for avoiding to
solve the wrong problem
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Software Development
Method
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Example
– Problem:
Compute and display the total cost of apples given the number
of pounds of apples and the cost per pound of apples
– Analysis:
• Inputs:
– Quantity of apples in pounds
– Cost per pound
• Output:
– Total costs (in dollars)
• Main formula:
– Total cost = Cost per pound * Pounds of apples
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Software Development
Method
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Design
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Problem solving step
Decompose into smaller problems
Top-down design (divide and conquer)
Develop Algorithm
• Algorithm: List of steps to solve a problem
• Algorithm refinement: Developing a sub-algorithm for a
particular step in the main algorithm
– Desk check
• Simulate the algorithm execution for simple interesting cases
using pencil and paper
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Software Development
Method
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Implementation
– Writing the algorithm in a special programming language e.g. C++
– Requires understanding the algorithmic notation as well as the
details of the respective programming language
Testing
– Verify that the program meets its requirements
– Unit test (only one sub-problem)
– System test (whole problem)
– Test coverage!
Documentation
– Key part in the development process
– Accompanying activity in each phase
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Software Development
Method
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Maintenance:
– Modify a program to remove errors
– Modify a program in order to extend it
– Initial programmer is very often not the person who
does maintenance!
– Understandability of code, use of guidelines
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Failure is a part of the process
– The step-by-step development help avoid failures
– But there are no guaranties
– Importance of documentation
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Software Development
Method
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Software engineering
– Area of computer science concerned with:
• Building large software systems
• Providing solutions for efficient and effective software
development
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Challenge
– Tremendous advances in hardware have not been
accompanied by comparable advances in software
– => Software crisis
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Software Engineering Goals
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Reliability
– An unreliable life-critical system can be fatal
– Software is in general more expensive and less reliable
than hardware
– E.g. Year 2000 problem
– Maintenance affects availability
Understandability
– Future development becomes very difficult if software
is hard to understand
Cost Effectiveness
– Cost to develop and maintain should not exceed profit
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Software Engineering Goals
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Adaptability
– Ease of modification in the program or in its environment
– System that is adaptive is easier to alter and expand
Reusability
– Reduces development costs
– Improves reliability and maintainability
– (Exception: Reuse of unreliable software)
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1.6 Applying the Software
Development Method
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Case Study:
Converting Miles to Kilometers
– Problem Your summer surveying job requires you to
study some maps that give distances in kilometers and
some that use miles. You and your coworkers prefer to
deal in metric measurements. Write a program that
performs the necessary conversion.
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Applying the Software
Development Method
– Analysis The first step in solving this problem
is to determine what you are asked to do. You
must convert from one system of measurement
to another, but are you supposed to convert
from kilometers to miles, or vice versa? The
problem states that you prefer to deal in metric
measurements, so you must convert distance
measurements in miles to kilometers.
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Applying the Software
Development Method
– Design The next step is to formulate the algorithm that
solves the problem. Begin by listing the three major
steps, or sub problems, of the algorithm.
• 1. Get distance in miles
• 2. Convert to kilometers
• 3. Display distance in kilometers
Refinement of step 2:
• The distance in kilometers is 1.609 times the distance in miles
Desk check
• 10 miles * 1.609 = 16.09 km (this would be displayed)
– Implementation To implement the solution, you must
write the algorithm as a C++ program.
– Testing How do you know the sample run is correct?
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Applying the Software
Development Method
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C++ code:
#include <iostream>
Using namespace std<
int main() {
const Km_Per_Mile = 1.609;
float miles, kms;
// Get distance in miles
cout << “Enter distance in miles: ”;
cin >> miles;
// convert to kilometers
kms = Km_Per_Mile * miles;
// display distance in kilometers
cout << “The distance in kms is “ << kms << endl;
return 0;
}
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1.7 Professional Ethics for
Computer Programmers
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Privacy and Misuse of Data
– Falsifying data in a database
– Computer thefts
Computer Hacking
– Breaking secure systems e.g. for amusement
– Spreading viruses in a network
Plagiarism and Software Piracy
– Using foreign programs without permission
– Violating copyright agreements
Misuse of a Computer Resource
– Illegal sharing of accounts and passwords in order to access special
systems and databases
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1.8 Summary
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History
– 1930 first computer
– Eniac: programmed by hand
– Von-Neumann: stored program concept
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Components of computers
– CPU (Central processing unit)
• Control Unit
• Arithmetic and Logic Unit (ALU)
– Main Memory
• Addresses
• Data: Bytes, Bits, Words
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1.8 Summary
– Secondary storage (unit is file)
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Disks
Tapes
Floppy
CDs
Removable disks
– I/O devices
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Keyboard (i)
Monitor (o)
Printer (o)
Modem (i/o)
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1.8 Summary
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Computer networks
– LAN
– WAN
– WWW
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Software
– Operating system
– Compilers
– Application software
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1.8 Summary
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Programming Languages
– High level language (e.g. procedural, oo, logic,
functional)
– Assembly language
– Machine language
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Tools for program development
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Editor
Compiler
Linker
Loader
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1.8 Summary
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Basic concepts of OO programming
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Class
Object
Method
Abstraction
Encapsulation
Modularity
Hierarchy
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1.8 Summary
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Basic steps of software development
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Specification of the problem
Analysis
Design
Implementation
Test
Maintenance
Failures !
Software Engineering Goals (e.g. reliability, cost
effectiveness, reusability)
Ethics in the use of computers
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