2001 prentice hall, inc. all rights reserved. chapter 1 – introduction to computers, the internet...
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![Page 1: 2001 Prentice Hall, Inc. All rights reserved. Chapter 1 – Introduction to Computers, the Internet and the World Wide Web Outline 1.1Introduction 1.2What](https://reader036.vdocuments.us/reader036/viewer/2022082821/5697bfda1a28abf838cb010a/html5/thumbnails/1.jpg)
2001 Prentice Hall, Inc. All rights reserved.
Chapter 1 – Introduction toComputers, the Internet and the World Wide
WebOutline1.1 Introduction1.2 What is a Computer?1.3 Computer Organization1.4 Evolution of Operating Systems1.5 Personal Computing, Distributed Computing and
Client/ Server Computing1.6 Machine Languages, Assembly Languages and
High-level Languages1.7 Structured Programming1.8 Object-Oriented Programming1.9 Hardware Trends1.10 History of the Internet1.11 History of the World Wide Web1.12 History of Perl
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2001 Prentice Hall, Inc. All rights reserved.
Chapter 1 – Introduction toComputers, the Internet and the World Wide
WebOutline1.13 Perl Library1.14 General Notes About Perl and This Book
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2001 Prentice Hall, Inc. All rights reserved.
1.1 Introduction
• We will learn– How to use Perl with the Common Gateway Interface
(CGI) for building dynamic, Web-based applications
• This course is appropriate for– Novices with little or no programming experience – Experienced professionals building substantial
information systems
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2001 Prentice Hall, Inc. All rights reserved.
1.2 What is a Computer?
• Computer – Device capable of performing computations and
making logical decisions– Computers process data under the control of sets of
instructions called computer programs
• Hardware – Various devices comprising a computer– Keyboard, screen, mouse, disks, memory, CD-ROM,
and processing units
• Software – Programs that run on a computer
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2001 Prentice Hall, Inc. All rights reserved.
1.3 Computer Organization
• Logical units of a computer– Input unit– Output unit– Memory unit– Arithmetic and logic unit (ALU)– Central processing unit (CPU)– Secondary storage unit
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2001 Prentice Hall, Inc. All rights reserved.
1.4 Evolution of Operating Systems
• Batch processing in early systems• Operating systems
– Early systems increased throughput– Multiprogramming
• “Simultaneous” operation of many jobs
– Timesharing• Many users sharing a computer at once• Development of UNIX
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2001 Prentice Hall, Inc. All rights reserved.
1.5 Personal Computing, Distributed Computing, and Client/Server
Computing• Personal computers
– Economical enough for individual
• Distributed computing – Computing distributed over networks
• Client/server computing– Sharing of information across computer networks
between file servers and clients (personal computers)
![Page 8: 2001 Prentice Hall, Inc. All rights reserved. Chapter 1 – Introduction to Computers, the Internet and the World Wide Web Outline 1.1Introduction 1.2What](https://reader036.vdocuments.us/reader036/viewer/2022082821/5697bfda1a28abf838cb010a/html5/thumbnails/8.jpg)
2001 Prentice Hall, Inc. All rights reserved.
1.6 Machine Languages, Assembly Languages and High-level Languages
• Three types of programming languages1. Machine languages
• Strings of numbers giving machine specific instructions• Example:
+1300042774+1400593419+1200274027
2. Assembly languages• English-like abbreviations representing elementary computer
operations (translated via assemblers)• Example:
LOAD BASEPAYADD OVERPAYSTORE GROSSPAY
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2001 Prentice Hall, Inc. All rights reserved.
1.6 Machine Languages, Assembly Languages and High-level Languages
3. High-level languages• Codes similar to everyday English• Use mathematical notations (translated via compilers)• Example:
grossPay = basePay + overTimePay
• Other high-level languages– FORTRAN
• Used for scientific and engineering applications
– COBOL • Used to manipulate large amounts of data
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2001 Prentice Hall, Inc. All rights reserved.
1.7 Structured Programming
• Structured programming – Disciplined approach to writing programs– Clear, easy to test and debug and easy to modify
• Development of programming languages– Pascal
• Designed for teaching structured programming
– C• Developed for writing systems software and compilers
– Ada• Developed to meet the needs of the Department of Defense• Multitasking
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2001 Prentice Hall, Inc. All rights reserved.
1.8 Object-Oriented Programming
• Software reuse• Programs more understandable and easier to
maintain• History
– Dates back to at least mid 1960s– Development of C++
• Added capabilities to create and manipulate objects
– Development of Java in early 1990s– Completely object-oriented language
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2001 Prentice Hall, Inc. All rights reserved.
1.9 Hardware Trends
• Improving technologies– Internet community thrives on improvements of
• Hardware• Software• Communications
– Cost of products and services • Consistently dropping over the decades
– Computer capacity and speed • Doubles every two years (on average)
– Microprocessor chip• Laid groundwork in late 1970s and 1980s for productivity
improvements of the 1990s
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2001 Prentice Hall, Inc. All rights reserved.
1.10 History of the Internet
• The Internet enables– Quick and easy communication via e-mail– International networking of computers
• Packet switching– The transfer of digital data via small packets– Allows multiple users to send and receive data
simultaneously• No centralized control
– If one part of the Internet fails, other parts can still operate
• Bandwidth – Information carrying capacity of communications lines
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2001 Prentice Hall, Inc. All rights reserved.
1.11 History of the World Wide Web
• WWW– Allows computer users to locate and view multimedia-
based documents – Introduced in 1990 by Tim Berners-Lee
• Internet today– Mixes computing and communications technologies– Makes information constantly and instantly available to
anyone with a connection
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2001 Prentice Hall, Inc. All rights reserved.
1.12 History of Perl
• Developed by Larry Wall in 1987– Aimed to integrate features of the UNIX languages awk
and sed with framework provided by shell
• Gained support in open-source community• Versions of Perl
– Perl 3• Adopted GNU General Public License
– Perl 4• Adopted Artistic License to attract more users
– Perl 5• Major reorganization of Perl language
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2001 Prentice Hall, Inc. All rights reserved.
1.12 History of Perl
– Perl 6• Development announced on July 18, 2000• Will be a complete rewrite of internals and externals of Perl
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2001 Prentice Hall, Inc. All rights reserved.
1.13 Perl Library
• Perl modules– Reusable pieces of software– Defined in library files ending in .pm– Primary distribution center is the Comprehensive Perl
Archive Network (CPAN)
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2001 Prentice Hall, Inc. All rights reserved.
1.13 General Notes About Perl and This Book
• Perl approach to programming– Qualities of a good programmer
• Laziness– Reusable code
• Impatience– Functional programs
• Hubris– Easy to understand code
– Programs can be written in many different ways– Highly portable