1.  2001 Prentice Hall, Inc. All rights reserved.
Chapter 1 – Introduction to Computers, the Internet and the World Wide Web
Outline 1.1 Introduction 1.2 What is a Computer? 1.3 Computer Organization
1.4 Evolution of Operating Systems
1.5 Personal Computing, Distributed Computing and Client/ Server Computing
1.6 Machine Languages, Assembly Languages and High-level Languages
1.7 Structured Programming
1.8 Object-Oriented Programming
1.9 Hardware Trends
1.10 History of the Internet
1.11 History of the World Wide Web 1.12 History of Perl
 2001 Prentice Hall, Inc. All rights reserved.

2.  2001 Prentice Hall, Inc. All rights reserved.
Chapter 1 – Introduction to Computers, the Internet and the World Wide Web
Outline 1.13 Perl Library
1.14 General Notes About Perl and This Book
 2001 Prentice Hall, Inc. All rights reserved.

3.  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
 2001 Prentice Hall, Inc. All rights reserved.

4.  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
 2001 Prentice Hall, Inc. All rights reserved.

5. 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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6. 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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7.  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)
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8. 1.6 Machine Languages, Assembly Languages and High-level Languages
Three types of programming languages
Machine languages
Strings of numbers giving machine specific instructions
Example:
Assembly languages
English-like abbreviations representing elementary computer operations (translated via assemblers)
LOAD BASEPAY
ADD OVERPAY
STORE GROSSPAY
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9. 1.6 Machine Languages, Assembly Languages and 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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10. 1.7 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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11. 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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12.  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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13. 1.10 History of the Internet
The Internet enables
Quick and easy communication via
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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14. 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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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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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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17.  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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18. 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
 2001 Prentice Hall, Inc. All rights reserved.