Introduction to C Language chapter 01.ppt

 2000 Prentice Hall, Inc. All rights reserved.
Chapter 1 – Introduction to Computers
and C++ Programming
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 The History of C
1.8 The C Standard Library
1.9 The Key Software Trend: Object Technology
1.10 C++ and C++ How to Program
1.11 Java and Java How to Program
1.12 Other High-level Languages
1.13 Structured Programming
1.14 The Basics of a 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 General Notes About C and this Book

1.1 Introduction
– We will learn the C programming language
– Learn structured programming and proper programming
techniques
– Chapter 15 - Introduction to C++, a superset of C (more later)
– 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

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

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

1.4 Evolution of 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
• Multiprogramming
– Many jobs or tasks sharing the computer resources
• Timesharing
– Runs a small portion of one user’s job then moves on to service
the next user

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)

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

1.6 Machine Languages, Assembly
Languages, and High-level Languages (II)
3. High-level languages
– Similar to everyday English and use mathematical notations
(translated via compilers)
– Example:
grossPay = basePay + overTimePay

1.7 History of C
• C
– Evolved by Ritchie from two previous programming languages,
BCPL and B
– Used to develop UNIX
– Now, most operating systems written with C or C++
– Hardware independent (portable)
– By late 1970's C had evolved to "Traditional C"
• Standardization
– Many slight variations of C existed, and were in compatible
– Committee formed to create a "unambiguous, machine-
independent" definition
– Standard created in 1989, updated in 1999

1.8 The 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 premade function exists, generally best to use it rather than
write your own
• Library functions carefully written, efficient, and portable

1.9 The 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

1.10 C++ and C++ How to Program
• C++
– Superset of C developed by Bjarne Stroustrup at Bell Labs
– "Spruces up" C, and provides object-oriented capabilities
• Objects - reuseable software components
– Object-oriented design very powerful
• 10 to 100 fold increase in productivity
– Dominant language in industry and university
• Learning C++
– Because C++ includes C, some feel it is best to master C,
then learn C++
– Starting in Chapter 15, we begin our introduction to C++

1.11 Java and Java How to Program
• 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

1.12 Other High-level Languages
• A few other high-level languages have achieved
broad acceptance
• FORTRAN
– Scientific and engineering applications
• COBOL
– Used to manipulate large amounts of data
• Pascal
– Intended for academic use

1.13 Structured Programming
• Structured programming
– Disciplined approach to writing programs
– Clear, easy to test and debug, and easy to modify
• Multitasking
– Specifying that many activities run in parallel

1.14 Basics of a Typical C Program
Development Environment
• Phases of C++ Programs:
1. Edit
2. Preprocess
3. Compile
4. Link
5. Load
6. Execute
Loader
Primary
Memory
Program is created in
the editor and stored
on disk.
Preprocessor program
processes the code.
Loader puts program
in memory.
CPU takes each
instruction and
executes it, possibly
storing new data
values as the program
executes.
Compiler
Compiler creates
object code and stores
it on disk.
Linker links the object
code with the libraries,
creates a.out and
stores it on disk
Editor
Preprocessor
Linker
CPU
Primary
Memory
.
.
.
.
.
.
.
.
.
.
.
.
Disk
Disk
Disk
Disk
Disk

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) to
hold programs and data over the longer term
– Processor speeds at which computers execute their
programs

1.16 History of the Internet
• The Internet enables
– Quick and easy communication via e-mail
– International networking of computers
• Packet switching
– Transfer 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

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

1.18 General Notes About C
and This Book
• Program clarity
– Programs that are convoluted 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
• We will do a careful walkthrough of C
– Some details and subtleties not covered
– If you need additional technical details
• Read the C standard document
• Read the book by Kernigan and Ritchie

Introduction to C Language chapter 01.ppt

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Introduction to C Language chapter 01.ppt