Introduction to Computer Networks and Networking
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Introduction to Computer Networks.
Introduction to Computer Networks and Networking
- 1. KIIT 2014 1 Introduction to Computer Networks
- 2. KIIT 2014 Objectives After completing this lesson, you should be able to do the following: • Introduction to Computer Networks • Evolution of Networking • Types of Networks • Network Devices • Networking Topologies • Define Node in the Network • Use of Internet and WEB • Define DNS
- 3. KIIT 2014 Introduction to Computer Networks • Information is being produced, exchanged, and traced across the globe in real time. It's possible as almost everyone and everything in the digital world is interconnected through one way or the other. • A group of two or more similar things or people interconnected with each other is called network. • Examples of network in our daily life: – Social network – Mobile network – Network of computers – Airlines, railway, banks, hospitals networks
- 4. KIIT 2014 Introduction to Computer Networks • A computer network is an interconnection among two or more computers or computing devices. • A basic network may connect a few computers placed in a room. The network size may vary from small to large depending on the number of computers it connects. • A computer network can include different types of hosts (also called nodes) like server, desktop, laptop, cellular phones.
- 5. KIIT 2014 Why Use C? • Mainly because it produces code that runs nearly as fast as code written in assembly language. Some examples of the use of C might be: – Operating Systems – Language Compilers – Assemblers – Text Editors – Network Drivers – Modern Programs – Data Bases – Language Interpreters – Utilities
- 6. KIIT 2014 History of C • Evolved from two previous languages – BCPL , B • BCPL (Basic Combined Programming Language) used for writing OS & compilers • B used for creating early versions of UNIX OS • Both were “typeless” languages • C language evolved from B (Dennis Ritchie – Bell labs) ** Typeless – no datatypes. Every data item occupied 1 word in memory.
- 7. KIIT 2014 History of C • In 1972 Dennis Ritchie at Bell Labs writes C and in 1978 the publication of The C Programming Language by Kernighan & Ritchie caused a revolution in the computing world • In 1983, the American National Standards Institute (ANSI) established a committee to provide a modern, comprehensive definition of C. The resulting definition, the ANSI standard, or "ANSI C", was completed late 1988.
- 8. KIIT 2014 Capabilities of C • Low Level Language Features • Portability • Powerful • Bit Manipulation • High Level Language Features • Modular Programming • Efficient use of Pointers
- 9. KIIT 2014 Software Development Method • Requirement Specification – Problem Definition • Analysis – Refine, Generalize, Decompose the problem definition • Design – Develop Algorithm • Implementation – Write Code • Verification and Testing – Test and Debug the code
- 10. KIIT 2014 Development with C • Four stages – Editing: Writing the source code by using some IDE or editor – Preprocessing or libraries: Already available routines – Compiling: translates or converts source to object code for a specific platform source code -> object code – Linking: resolves external references and produces the executable module • Portable programs will run on any machine Note: Program correctness and robustness are most important than program efficiency
- 11. KIIT 2014 Programming languages • Various programming languages • Some understandable directly by computers • Others require “translation” steps – Machine language • Natural language of a particular computer • Consists of strings of numbers(1s, 0s) • Instruct computer to perform elementary operations one at a time • Machine dependant
- 12. KIIT 2014 Programming languages • Assembly Language – English like abbreviations – Translators programs called “Assemblers” to convert assembly language programs to machine language – E.g. add overtime to base pay and store result in gross pay LOAD BASEPAY ADD OVERPAY STORE GROSSPAY
- 13. KIIT 2014 Programming languages • High-level languages – To speed up programming even further – Single statements for accomplishing substantial tasks – Translator programs called “Compilers” to convert high-level programs into machine language – E.g. add overtime to base pay and store result in gross pay grossPay = basePay + overtimePay
- 14. KIIT 2014 C Standard Library • Two parts to learning the “C” world – Learn C itself – Take advantage of rich collection of existing functions called C Standard Library • Avoid reinventing the wheel • SW reusability
- 15. KIIT 2014 Basics of C Environment • C systems consist of 3 parts – Environment – Language – C Standard Library • Development environment has 6 phases – Edit – Pre-processor – Compile – Link – Load – Execute
- 16. KIIT 2014 Basics of C Environment Editor Disk Phase 1 Program edited in Editor and stored on disk Preprocessor Disk Phase 2 Preprocessor program processes the code Compiler Disk Phase 3 Creates object code and stores on disk Linker Disk Phase 4 Links object code with libraries and stores on disk
- 17. KIIT 2014 Basics of C Environment Loader Phase 5 Puts program in memory Primary memory CPU Phase 6 Takes each instruction and executes it storing new data values Primary memory
- 18. KIIT 2014 C Program Example A C program basically consists of the following parts: • Preprocessor Commands • Functions • Variables • Statements & Expressions • Comments
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- 20. KIIT 2014 Simple C Program /* A first C Program*/ #include <stdio.h> void main() { printf("Hello World n"); }
- 21. KIIT 2014 Simple C Program • Line 1: #include <stdio.h> – As part of compilation, the C compiler runs a program called the C preprocessor. The preprocessor is able to add and remove code from your source file. – In this case, the directive #include tells the preprocessor to include code from the file stdio.h. – This file contains declarations for functions that the program needs to use. A declaration for the printf function is in this file.
- 22. KIIT 2014 Simple C Program • Line 2: void main() – This statement declares the main function. – A ‘C’ program can contain many functions but must always have one main function. – A function is a self-contained module of code that can accomplish some task. – Functions are examined later. – The "void" specifies the return type of main. In this case, nothing is returned to the operating system.
- 23. KIIT 2014 Simple C Program • Line 3: { – This opening bracket denotes the start of the program.
- 24. KIIT 2014 Simple C Program • Line 4: printf("Hello World n"); – printf is a function from a standard C library that is used to print strings to the standard output, normally your screen. – The compiler links code from these standard libraries to the code you have written to produce the final executable. – The "n" is a special format modifier that tells the printf to put a line feed at the end of the line. – If there were another printf in this program, its string would print on the next line.
- 25. KIIT 2014 Simple C Program • Line 5: } – This closing bracket denotes the end of the program.
- 26. KIIT 2014 Compile & Execute C Program Following are the simple steps: • Open a text editor and add the above-mentioned code. • Save the file as hello.c • Open a command prompt and go to the directory where you saved the file. • Type gcc hello.c and press enter to compile your code. • If there are no errors in your code, the command prompt will take you to the next line and would generate a.out executable file. • Now, type a.out to execute your prog ram. • You will be able to see "Hello World" printed on the screen
- 27. KIIT 2014 Summary In this lesson, you should have learned how to: • Define C language • List the capabilities of C language • Define Software Development Method • Develop software with C • Write programs in different types of Languages • Write Simple C Program • Compile & Execute C Program
- 28. KIIT 2014 Escape Sequence • n new line • t tab • r carriage return • a alert • backslash • ” double quote
- 29. KIIT 2014 Memory concepts • Every variable has a name, type and value • Variable names correspond to locations in computer memory • New value over-writes the previous value– “Destructive read-in” • Value reading called “Non-destructive read- out”
- 30. KIIT 2014 Arithmetic in C C operation Algebric C Addition(+) f+7 f+7 Subtraction (-) p-c p-c Multiplication(*) bm b*m Division(/) x/y, x , x y x/y Modulus(%) r mod s r%s
- 31. KIIT 2014 Precedence order • Highest to lowest – () – *, /, % – +, -
- 32. KIIT 2014 Example Algebra: z = pr%q+w/x-y C: z = p * r % q + w / x – y ; Precedence: 1 2 4 3 5
- 33. KIIT 2014 Example Algebra: a(b+c)+ c(d+e) C: a * ( b + c ) + c * ( d + e ) ; Precedence: 3 1 5 4 2
- 34. KIIT 2014 Decision Making • Checking falsity or truth of a statement • Equality operators have lower precedence than relational operators • Relational operators have same precedence • Both associate from left to right
- 35. KIIT 2014 Decision Making • Equality operators – == – != • Relational operators – < – > – <= – >=
- 36. KIIT 2014 Summary of precedence order Operator Associativity () left to right * / % left to right + - left to right < <= > >= left to right == != left to right = left to right
- 37. KIIT 2014 Assignment operators • = • += • -= • *= • /= • %=
- 38. KIIT 2014 Increment/ decrement operators • ++ ++a • ++ a++ • -- --a • -- a--
- 39. KIIT 2014 Increment/ decrement operators main() { int c; c = 5; printf(“%dn”, c); printf(“%dn”, c++); printf(“%dnn”, c); c = 5; printf(“%dn”, c); printf(“%dn”, ++c); printf(“%dn”, c); return 0; }
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