Lecture 1.ppt

 2007 Pearson Education, Inc. All rights reserved.
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Introduction to Computers, the Internet
and the Web
By
Mr. Joseph Wanambwa
Tel: +256703600655
Email: josephwanambwa@gmail.com
PROGRAMMING METHODOLOGIES:

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OBJECTIVES
In this chapter you will learn:
 Basic computer concepts.
 The different types of programming languages.
 The history of the C programming language.
 The purpose of the C Standard Library.
 The elements of a typical C program development
environment.
 Why it is appropriate to learn C in a first programming
course.
 How C provides a foundation for further study of
programming languages in general and of C++, Java
and C# in particular.
 The history of the Internet and the World Wide Web.

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1.1 Introduction
1.2 What Is a Computer?
1.3 Computer Organization
1.4 Early Operating Systems
1.5 Personal, Distributed and Client/Server Computing
1.6 Machine Languages, Assembly Languages and
High-Level Languages
1.7 Fortran, COBOL, Pascal and Ada
1.8 History of C
1.9 C Standard Library

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1.10 C++
1.11 Java
1.12 BASIC, Visual Basic, Visual C++, Visual C# and .NET
1.13 Key Software Trend: Object Technology
1.14 Typical C Program Development Environment
1.15 Hardware Trends
1.16 History of the Internet
1.17 History of the World Wide Web
1.18 Notes About C
1.19 Web Resources

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1.1 Introduction
 We will learn
– The C programming language
– Structured programming and proper programming
techniques
 This course is appropriate for
– Technically oriented people with little or no programming
experience
– Experienced programmers who want a deep and rigorous
treatment of the language

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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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1.3 Computer Organization
 Six logical units in every computer:
1. Input unit
- Obtains information from input devices (keyboard, mouse)
2. Output unit
- Outputs information (to screen, to printer, to control other devices)
3. Memory unit
- Rapid access, low capacity, stores input information
4. Arithmetic and logic unit (ALU)
- Performs arithmetic calculations and logic decisions
5. Central processing unit (CPU)
- Supervises and coordinates the other sections of the computer
6. Secondary storage unit
- Cheap, long-term, high-capacity storage
- Stores inactive programs

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1.4 Early Operating Systems
 Batch processing
– Do only one job or task at a time
 Operating systems
– Manage transitions between jobs
– Increased throughput
- Amount of work computers process
 Multitasking
– Computer resources are shared by many jobs or tasks
 Timesharing
– Computer runs a small portion of one user’s job then moves on
to service the next user

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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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1.6 Machine Languages, Assembly
Languages, and High-level Languages
Three types of programming languages
1. 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 BASEPAY
ADD OVERPAY
STORE GROSSPAY

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1.6 Machine Languages, Assembly
Languages, and High-level Languages
Three types of programming languages (continued)
3. High-level languages
- Codes similar to everyday English
- Use mathematical notations (translated via compilers)
- Example:
grossPay = basePay + overTimePay

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 Fortran
– developed by IBM Corporation in the 1950s
– used for scientific and engineering applications that
require complex mathematical computations
 COBOL
– developed in 1959 by computer manufacturers, the
government and industrial computer users
– used for commercial applications that require precise and
efficient manipulation of large amounts of data

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 Pascal
– Developed by Professor Niklaus Wirth in 1971
– Designed for teaching structured programming
 Ada
– Developed under the sponsorship of the U.S. Department
of Defense (DOD) during the 1970s and early 1980s
– Able to perform multitasking

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1.8 History of C
 C
– Evolved by Ritchie from two previous programming languages,
BCPL and B. BCPL ("Basic Combined Programming
Language") is a procedural, imperative, and structured
computer programming language. B was derived from BCPL.
– Used to develop UNIX
– Used to write modern operating systems
– Hardware independent (portable)
– By late 1970's C had evolved to "Traditional C"
 Standardization
– Many slight variations of C existed, and were incompatible
– Committee formed to create a "unambiguous, machine-
independent" definition
– Standard created in 1989, updated in 1999

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Portability Tip 1.1
Because C is a hardware-independent, widely
available language, applications written in C
can run with little or no modifications on a wide
range of different computer systems.

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1.9 C Standard Library
 C programs consist of pieces/modules called
functions
– A programmer can create his own functions
- Advantage: the programmer knows exactly how it works
- Disadvantage: time consuming
– Programmers will often use the C library functions
- Use these as building blocks
– Avoid re-inventing the wheel
- If a pre-made function exists, generally best to use it rather
than write your own
- Library functions carefully written, efficient, and portable

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Performance Tip 1.1
Using Standard C library functions instead
of writing your own comparable versions can
improve program performance, because these
functions are carefully written to perform
efficiently.

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Portability Tip 1.2
Using Standard C library functions instead
of writing your own comparable versions can
improve program portability, because these
functions are used in virtually all Standard C
implementations.

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1.10 C++
 C++
– Superset of C developed by Bjarne Stroustrup at Bell Labs
– "Spruces up" C, and provides object-oriented capabilities
– Dominant language in industry and academia
 Learning C++
– Because C++ includes C, some feel it is best to master C,
then learn C++

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1.11 Java
 Java is used to
– Create Web pages with dynamic and interactive content
– Develop large-scale enterprise applications
– Enhance the functionality of Web servers
– Provide applications for consumer devices (such as cell
phones, pagers and personal digital assistants)
 Java How to Program
– Closely followed the development of Java by Sun
– Teaches first-year programming students the essentials of
graphics, images, animation, audio, video, database,
networking, multithreading and collaborative computing

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1.12 BASIC, Visual Basic, Visual C++,
Visual C# and .NET
 BASIC
– Developed in the mid-1960s by Professors John Kemeny
and Thomas Kurtz of Dartmouth College as a language for
writing simple programs
 Visual Basic
– Introduced by Microsoft in 1991 to simplify the process of
making Windows applications
 Visual Basic, Visual C++, and Visual C#
– Designed for Microsoft’s .NET programming platform

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1.13 Key Software Trend: Object
Technology
 Objects
– Reusable software components that model items in the real
world
– Meaningful software units
- Date objects, time objects, paycheck objects, invoice objects,
audio objects, video objects, file objects, record objects, etc.
- Any noun can be represented as an object
– Very reusable
– More understandable, better organized, and easier to
maintain than procedural programming
– Favor modularity

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1.14 Typical C Program Development
Environment
Phases of C++ Programs:
–Editor
–Preprocess
–Compile: creates the object
code
–Link: links object code with
the libraries and then creates
an executable
–Load: puts program in
memory
–Execute: CPU takes each
instruction and executes it
Fig. 1.1 | Typical C development environment.

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Common Programming Error 1.1
Errors like division-by-zero occur as a program
runs, so these errors are called runtime errors or
execution-time errors. Divide-by-zero is generally a
fatal error, i.e., an error that causes the program to
terminate immediately without successfully
performing its job. Nonfatal errors allow programs
to run to completion, often producing incorrect
results. [Note: On some systems, divide-by-zero is not
a fatal error. Please see your system documentation.]

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1.15 Hardware Trends
 Every year or two the following approximately
double:
– Amount of memory in which to execute programs
– Amount of secondary storage (such as disk storage)
- Used to hold programs and data over the longer term
– Processor speeds
- The speeds at which computers execute their programs

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1.16 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
 TCP/IP
 Bandwidth
– Information carrying capacity of communications lines

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1.17 History of the World Wide Web
 World Wide Web
– Locate and view multimedia-based documents on almost
any subject
– Makes information instantly and conveniently accessible
worldwide
– Possible for individuals and small businesses to get
worldwide exposure
– Changing the way business is done

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1.18 General Notes About C
 Program clarity
– Programs that are complex are difficult to read,
understand, and modify
 C is a portable language
– Programs can run on many different computers
– However, portability is an elusive goal
– are not covered
 Reference
- C by Example By Greg Perry

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Good Programming Practice 1.1
Write your C programs in a simple and
straightforward manner. This is sometimes
referred to as KIS (“keep it simple”). Do not
“stretch” the language by trying bizarre usages.

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Portability Tip 1.3
Although it is possible to write portable
programs, there are many problems
between different C compilers and different
computers that make portability difficult to
achieve. Simply writing programs in C does
not guarantee portability. The progammer
will often need to deal directly with complex
computer variations.

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Read the manuals for the version of C you
are using. Reference these manuals
frequently to be sure you are aware of the
rich collection of C features and that you are
using these features correctly.
Software Engineering Observation 1.1

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Software Engineering Observation 1.2
Your computer and compiler are good
teachers. If you are not sure how a feature
of C works, write a sample program with
that feature, compile and run the program
and see what happens.

Lecture 1.ppt

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