About the Presentations
• The presentations cover the objectives found in the opening of each chapter.
• All chapter objectives are listed in the beginning of each presentation.
• You may customize the presentations to fit your class needs.
• Some figures from the chapters are included. A complete set of images from the book can be found on the Instructor Resources disc.
Invitation to Computer Science, 5th Edition
Objectives
In this chapter, you will learn about:
• The definition of computer science
• Algorithms
• A brief history of computing
• Organization of the text
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Invitation to Computer Science, 5th Edition
Introduction
• Misconceptions – Computer science is:
• The study of computers
• The study of how to write computer programs
• The study of the uses and applications of computers and software
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Invitation to Computer Science, 5th Edition
The Definition of Computer Science
• Computer science is the study of algorithms, including:– Their formal and mathematical properties– Their hardware realizations– Their linguistic realizations– Their applications
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Invitation to Computer Science, 5th Edition
The Definition of Computer Science (continued)
• Algorithm– Step-by-step method for accomplishing some task
• Operations used to construct algorithms– Sequential operations– Conditional operations– Iterative operations
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Invitation to Computer Science, 5th Edition
Figure 1.1 Programming Your DVR. An Example of an Algorithm
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Invitation to Computer Science, 5th Edition
The Definition of Computer Science (continued)
• Why are formal algorithms so important in computer science? – If we can specify an algorithm to solve a problem,
then we can automate its solution
• Computing agent– Machine, robot, person, or thing carrying out the
steps of the algorithm
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Invitation to Computer Science, 5th Edition
Algorithms
• Algorithm– Well-ordered collection of unambiguous and
effectively computable operations that, when executed, produces a result and halts in a finite amount of time
• Ambiguous statements– Go back and do it again (Do what again?)– Start over (From where?)
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Invitation to Computer Science, 5th Edition
Algorithms (continued)
• Unambiguous operation– Can be understood and carried out directly by the
computing agent without further simplification or explanation
– Also called primitive operation
• It is not enough for an operation to be understandable– It must also be doable (effectively computable) by
the computing agent
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Invitation to Computer Science, 5th Edition
Algorithms (continued)
• Algorithm– Result must be produced after the execution of a
finite number of operations
• Infinite loop– Runs forever
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Invitation to Computer Science, 5th Edition
Figure 1.3a A Correct Solution to the Shampooing Problem
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Invitation to Computer Science, 5th Edition
Figure 1.3b Another Correct Solution to the Shampooing Problem
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Invitation to Computer Science, 5th Edition
The Importance of Algorithmic Problem Solving
• “Computer revolution” of the twentieth and twenty-first centuries– Has enabled us to implement algorithms that
mechanize and automate the drudgery of repetitive mental tasks
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Invitation to Computer Science, 5th Edition
A Brief History of Computing
• The Early Period: Up to 1940– John Napier invented logarithms as a way to
simplify difficult mathematical computations– The first slide rule appeared around 1622– Blaise Pascal designed and built one of the first
mechanical calculators (named the Pascaline)– Gottfried Leibnitz constructed a mechanical
calculator called Leibnitz’s Wheel
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Invitation to Computer Science, 5th Edition
Figure 1.4 The Pascaline. One of the Earliest Mechanical Calculators
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Invitation to Computer Science, 5th Edition
The Early Period: Up to 1940
• Difference Engine– Could do addition, subtraction, multiplication, and
division to six significant digits– Could solve polynomial equations and other complex
mathematical problems
• Babbage’s Analytic Engine– Amazingly similar in design to a modern computer
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Invitation to Computer Science, 5th Edition
The Early Period: Up to 1940 (continued)
• Herman Hollerith– Designed and built programmable card-processing
machines that could automatically read, tally, and sort data entered on punched cards
– Founded the Computer Tabulating Recording Company
– In 1924, Hollerith’s tabulating machine company changed its name to IBM
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Invitation to Computer Science, 5th Edition
The Birth of Computers: 1940–1950
• Mark I– General-purpose, electromechanical programmable
computer that used a mix of relays, magnets, and gears to process and store data
• ENIAC (Electronic Numerical Integrator and Calculator)– Completed in 1946– First fully electronic general-purpose programmable
computer
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Invitation to Computer Science, 5th Edition
The Birth of Computers: 1940–1950 (continued)
• John Von Neumann– Proposed a radically different computer design
based on a model called the stored program computer
– Research group at the University of Pennsylvania built one of the first stored program computers, called EDVAC, in 1951
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Invitation to Computer Science, 5th Edition
The Modern Era: 1950 to the Present
• First generation of computing – 1950 to 1957
• Second generation (1957–1965)– Era of FORTRAN and COBOL– The occupation called programmer was born
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Invitation to Computer Science, 5th Edition
The Modern Era: 1950 to the Present (continued)
• Third generation (1965 to 1975)– Era of the integrated circuit– Birth of the first minicomputer– Birth of the software industry
• Fourth generation (1975 to 1985)– Saw the appearance of the first microcomputer and
computer network– Electronic mail became an important application
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Invitation to Computer Science, 5th Edition
The Modern Era: 1950 to the Present (continued)
• Fifth generation (1985–?)– Massively parallel processors capable of quadrillions
(1015) of computations per second– Handheld digital devices and other types of personal
digital assistants (PDAs)– High-resolution graphics for imaging, animation,
movie making, and virtual reality
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Invitation to Computer Science, 5th Edition
Figure 1.8 Some of the Major Advancements in Computing25
Invitation to Computer Science, 5th Edition
Organization of the Text
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Figure 1.9 Organization of the Text into a Six-Layer Hierarchy
Invitation to Computer Science, 5th Edition
Summary
• Computer science is the study of algorithms
• An algorithm is a well-ordered collection of unambiguous and effectively computable operations that, when executed, produces a result and halts in a finite amount of time
• If we can specify an algorithm to solve a problem, then we can automate its solution
• Computers developed from mechanical calculating devices to modern electronic marvels of miniaturization
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