1. MS Sadia Ejaz CIIT ATTOCK Lecture 5+6 Introduction to computer & programming MS SADIA EJAZ CS DEPARTMENT

2. MS Sadia Ejaz CIIT ATTOCK The Internet It is a huge network of computers, which links many different types of computers all over the world. It is a huge network of computers, which links many different types of computers all over the world. It is a network of networks, which share a common mechanism for addressing (identifying) computers, and a common set of communication protocols for communication between two computers on the network. It is a network of networks, which share a common mechanism for addressing (identifying) computers, and a common set of communication protocols for communication between two computers on the network. 2

3. MS Sadia Ejaz CIIT ATTOCK The Internet’s Major Services The World Wide Web The World Wide Web Electronic mail Electronic mail News News File Transfer Protocol File Transfer Protocol Chat Chat Instant Messaging Instant Messaging Online- Services Online- Services Peer-to-Peer Services Peer-to-Peer Services 3

4. MS Sadia Ejaz CIIT ATTOCK The World Wide Web The World Wide Web (commonly shortened to the Web) is a system of interlinked hypertext documents accessed via the Internet. The World Wide Web (commonly shortened to the Web) is a system of interlinked hypertext documents accessed via the Internet. With a Web browser, a user views Web pages that may contain text, images, videos, and other multimedia and navigates between them using hyperlinks. With a Web browser, a user views Web pages that may contain text, images, videos, and other multimedia and navigates between them using hyperlinks. 4

5. MS Sadia Ejaz CIIT ATTOCK Web Search Engine A Web search engine is a search engine designed to search for information on the World Wide Web. A Web search engine is a search engine designed to search for information on the World Wide Web. A search engine lets you search for information by typing one or more words. The engine then displays a list of Web pages that contain information related to your words. A search engine lets you search for information by typing one or more words. The engine then displays a list of Web pages that contain information related to your words. Example: Google search engine Example: Google search engine 5

6. E - Mail Electronic mail, often abbreviated to e-mail, is a store- and-forward method of writing, sending, receiving and saving messages over electronic communication systems. Electronic mail, often abbreviated to e-mail, is a store- and-forward method of writing, sending, receiving and saving messages over electronic communication systems. 6

7. MS Sadia Ejaz CIIT ATTOCK Programming Language Generations Machine languages: first generation Assembly languages: second generation Higher-level languages: third generation (3GLs)

8. MS Sadia Ejaz CIIT ATTOCK Fading Third-Generation Languages FORTRAN (FORmula TRANslator) COBOL (COmmon Business Oriented Language) BASIC (Beginner’s All-Purpose Symbolic Instruction Code) Pascal

9. MS Sadia Ejaz CIIT ATTOCK Thriving Third-Generation Languages C C++ Java ActiveX

10. MS Sadia Ejaz CIIT ATTOCK Fourth-Generation Languages (4GLs) Builds programs with a front end, which is an interface that hides much of the program from the user Provides prototypes, which are samples of the finished programs

11. MS Sadia Ejaz CIIT ATTOCK Examples of Fourth-Generation Languages Visual Basic (VB) VisualAge Authoring environments

12. MS Sadia Ejaz CIIT ATTOCK Fifth-Generation Languages (5GLs) Advanced authoring environments considered by some to be 5GLs

13. MS Sadia Ejaz CIIT ATTOCK World Wide Web Development Languages HyperText Markup Language (HTML) Extensible Markup Language (XML) Wireless Markup Language (WML) Dreamweaver Flash Director

14. MS Sadia Ejaz CIIT ATTOCK Systems Development Life Cycle for Programming Phase 1: Needs analysis Phase 2: Program design Phase 3: Development (also called coding) Phase 4: Implementation Phase 5: Maintenance

15. MS Sadia Ejaz CIIT ATTOCK Why We Do Programming ? For solving problems  Computers are used as a tool to solve complex problems by developing computer programs that provide the solution of the problems.  Example: Program : For adding 2 numbers, i.e 3 and 5 Solution: A computer program will be developed for their addition.

16. MS Sadia Ejaz CIIT ATTOCK Problem-Solving Techniques Program Algorithm Pseudo Code Flowchart, etc.

17. MS Sadia Ejaz CIIT ATTOCK Program A set of instructions that tells a computer what to do is called program. Computer programs are written in programming languages. A person who develops a program is called programmer.

18. MS Sadia Ejaz CIIT ATTOCK Algorithms It is a step-by-step procedure to solve a problem. Properties of Algorithm  The given problem should be broken down into simple and meaningful steps.  The steps should be numbered sequentially.  The steps should be descriptive and written in simple English.

19. MS Sadia Ejaz CIIT ATTOCK Pseudo Code / Pseudo Language Algorithms are written in a language, which is similar to simple English, which is known as pseudo language. The purpose of using pseudo code is that it may be easier for humans to read than conventional programming languages. No standard for pseudo code syntax exists, as a program in pseudo code is not an executable program.

20. MS Sadia Ejaz CIIT ATTOCK Parts of Program Development Two main parts  Logic Design  Coding

21. MS Sadia Ejaz CIIT ATTOCK Logic Design Logic of the program is designed by specifying different steps required and the sequence of these steps to solve the problem.

22. MS Sadia Ejaz CIIT ATTOCK Coding The algorithm is converted into a program.

23. MS Sadia Ejaz CIIT ATTOCK Example Algorithm for calculating and displaying the sum of two numbers, 1. Input A, B 2. Total / Sum A + B 3. Display Total 4. Exit

24. MS Sadia Ejaz CIIT ATTOCK Advantages of Algorithms Reduced Complexity Increased Flexibility Ease of Understanding

25. MS Sadia Ejaz CIIT ATTOCK Flowchart It is combination of two words i.e. flow and chart. Flowchart is a graphical representation of an algorithm.  Chart consists of different symbols to display information about any program.  Flow indicates the direction of processing that takes place in the program. It is used to show all the steps of an algorithm in a sequence.

26. MS Sadia Ejaz CIIT ATTOCK Flowchart (contd.)

27. MS Sadia Ejaz CIIT ATTOCK Uses of Logic Flowchart It is used to represent an algorithm in simple graphical manner. It is used to show the steps of an algorithm in an easy way. It is used to understand the flow of the program. It is used to improve the logic for solving a problem. Programs can be reviewed and debugged easily.

28. MS Sadia Ejaz CIIT ATTOCK Basic Flowchart Symbols Input/Output Parallelogram symbol is used to represent an input or output step. Input statement is used to get input from the user. The output statement is used to display a message to the use or to display a value. InputOutput

29. MS Sadia Ejaz CIIT ATTOCK Basic Flowchart Symbols (contd.) Process Rectangle symbol is used to represent a process step.

30. MS Sadia Ejaz CIIT ATTOCK Basic Flowchart Symbols (contd.) Selection Diamond symbol is used to represent a selection step.

31. MS Sadia Ejaz CIIT ATTOCK Basic Flowchart Symbols (contd.) Start/End Oval symbol is used to represent the start or end of the flowchart. Start End

32. MS Sadia Ejaz CIIT ATTOCK Basic Flowchart Symbols (contd.) Connector Indicates that the flow continues where a matching symbol (containing the same letter) has been placed.

33. MS Sadia Ejaz CIIT ATTOCK Basic Flowchart Symbols (contd.) Flow Line Lines indicate the sequence of steps and the direction of flow.

34. MS Sadia Ejaz CIIT ATTOCK Example Start End Sum = A+B Input A, B Display Sum

35. MS Sadia Ejaz CIIT ATTOCK Difference Between Pseudo Code and Flowchart FlowchartPseudo Code It contains standard symbols to represent different computer operations. There is no standard for writing pseudo code. It is less frequently used as it takes more time to design. It is more frequently used as it takes less time. It is difficult to modify.It is easier to modify. It is a graphical representation of solution. It is not a graphical representation of solution.

36. MS Sadia Ejaz CIIT ATTOCK Program Development Process A programmer has to go through the following stages to develop a computer program:  Defining and Analyzing the Problem.  Designing the Algorithm  Coding or Writing the Program  Test Execution  Debugging  Final Documentation

37. MS Sadia Ejaz CIIT ATTOCK Integrated Development Environment (IDE) Editor Editor Compilers Compilers Debugger Debugger Linkers Linkers Loaders Loaders

38. MS Sadia Ejaz CIIT ATTOCK 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 creates object code and stores it on disk. Linker links the object code with the libraries Loader Primary Memory Compiler Editor Preprocessor Linker Primary Memory........................ Disk CPU Disk Program is created in the editor and stored on disk.

39. MS Sadia Ejaz CIIT ATTOCK Tools of the trade  Editor First of all we need a tool for writing the code of a program. For this purpose we used Editors in which we write our code.

40. MS Sadia Ejaz CIIT ATTOCK Debugger It is used to debug the program. It is used to debug the program.

41. MS Sadia Ejaz CIIT ATTOCK Linker Most of the time our program is using different routines and functions that are located in different files, hence it needs the executable code of those routines/functions. Most of the time our program is using different routines and functions that are located in different files, hence it needs the executable code of those routines/functions. Linker is a tool which performs this job, it checks our program and includes all those routines or functions which we are using in our program to make a standalone executable code and this process is called Linking. Linker is a tool which performs this job, it checks our program and includes all those routines or functions which we are using in our program to make a standalone executable code and this process is called Linking.

42. MS Sadia Ejaz CIIT ATTOCK Loader Another process which is needed to load the program into memory and then instruct the processor to start the execution of the program from the first instruction (the starting point of every C program is from the main function). Another process which is needed to load the program into memory and then instruct the processor to start the execution of the program from the first instruction (the starting point of every C program is from the main function). This processor is known as loader. This processor is known as loader. Linker and loaders are the part of development environment. These are part of system software. Linker and loaders are the part of development environment. These are part of system software.

43. MS Sadia Ejaz CIIT ATTOCK Debugging in Turbo C++ An error in a computer program is known as bug. An error in a computer program is known as bug. The process of finding and removing bugs is known as debugging. The process of finding and removing bugs is known as debugging.

44. MS Sadia Ejaz CIIT ATTOCK Types of Errors Syntax Errors Syntax Errors Logical Errors Logical Errors Run-Time Errors Run-Time Errors

45. MS Sadia Ejaz CIIT ATTOCK Syntax Errors It is a type of error that occurs when an invalid statement is written in program. It is a type of error that occurs when an invalid statement is written in program.

46. MS Sadia Ejaz CIIT ATTOCK Logical Errors It is a type of error that occurs due to poor logic of the programmer. It is a type of error that occurs due to poor logic of the programmer.

47. MS Sadia Ejaz CIIT ATTOCK Run-Time Errors It is a type of error that occurs during the execution of program. It is a type of error that occurs during the execution of program.

48. MS Sadia Ejaz CIIT ATTOCK C++ Statement The statement of the program are writen under the main() function between the curely bracket{}. These statement are the body of program Each statement of the c++ ends with a semicolon(;) C++ is a case sensitive language The c++ statement are normally written in lowercase letters but in some exceptional but in some exceptional cases, these can also be written in upper case

49. MS Sadia Ejaz CIIT ATTOCK keyword The words that are used by the language for special purpose are called keywords e.g. in c++ program, the word main is used to indicate the starting of program, include is used to header files, int to declare an integer data type All these words are keyword of c++ The keyword cannot be used as variable names in program

50. MS Sadia Ejaz CIIT ATTOCK Identifiers The identifiers are the names used to represent variable, constants, types, functions and labels in the program. The identifiers are the names used to represent variable, constants, types, functions and labels in the program. An identifier in C++ may consist of 31 characters. An identifier in C++ may consist of 31 characters.

51. MS Sadia Ejaz CIIT ATTOCK Types of Identifiers Standard Identifiers Standard Identifiers  A type of identifier that has special meaning in C++ is known standard identifier.  For example. cout, cin, etc. User-defined Identifiers User-defined Identifiers  The type of identifier that is defined by the programmer to access memory location is known as user-defined identifier.  For example, marks, age, etc.

52. MS Sadia Ejaz CIIT ATTOCK Keywords Keyword is a word in C++ language that has a predefined meaning and purpose. Keyword is a word in C++ language that has a predefined meaning and purpose. They are also known as reserved words. They are also known as reserved words. The total number of keywords is 63. The total number of keywords is 63. For example, int, class, etc. For example, int, class, etc.

53. MS Sadia Ejaz CIIT ATTOCK Data Types The data type defines a set of values and a set of operations on these values. The data type defines a set of values and a set of operations on these values. A C++ program may need to process different types of data. A C++ program may need to process different types of data.

54. MS Sadia Ejaz CIIT ATTOCK Data Types Data TypePurpose Data TypePurpose intto store numeric values intto store numeric values floatto store real values floatto store real values doubleto store large real values doubleto store large real values charto store character values charto store character values

55. MS Sadia Ejaz CIIT ATTOCK Integer Data Type Integer data is numeric value with no decimal point or fraction. Integer data is numeric value with no decimal point or fraction. Types of IntegersSize in Bytes int 2 int 2 short int2 short int2 long int4 long int4 unsigned int2 unsigned int2 unsigned long int4 unsigned long int4

56. MS Sadia Ejaz CIIT ATTOCK Real Data Types Real data is numeric value with decimal point or fraction. Real data is numeric value with decimal point or fraction. It is also called floating point number. It is also called floating point number. Types of RealSize in Bytes Types of RealSize in Bytes float4 float4 double8 double8 long double10 long double10

57. MS Sadia Ejaz CIIT ATTOCK Character Data Type char data type is used to store character value. char data type is used to store character value. It takes 1 byte in memory. It takes 1 byte in memory. The characters are stored in ASCII code form. The characters are stored in ASCII code form. ASCII  American Standard Code for Information Interchange. ASCII  American Standard Code for Information Interchange.

58. MS Sadia Ejaz CIIT ATTOCK Integer Overflow and Underflow Integer Overflow Integer Overflow  It occurs when the value assigned to an integer variable is more than maximum possible value. Integer Underflow Integer Underflow  It occurs when the value assigned to an integer variable is less than possible minimum value.

59. MS Sadia Ejaz CIIT ATTOCK Variables A variable is a named memory location or memory cell. A variable is a named memory location or memory cell. The value stored in a variable is referred by variable name. The value stored in a variable is referred by variable name.

60. MS Sadia Ejaz CIIT ATTOCK Variables Declaration The process of specifying the variable name and its type is called variable declaration. The process of specifying the variable name and its type is called variable declaration. Syntax Syntax  Data typevariable_name ;  e.g. int marks ;

61. MS Sadia Ejaz CIIT ATTOCK Rules for Declaring Variables Variable may include letter, numbers and underscore (_). Variable may include letter, numbers and underscore (_). The first character of variable must be a letter or underscore _. The use of underscore is not recommended. The variables 9minute, #home and 2kg are invalid. The first character of variable must be a letter or underscore _. The use of underscore is not recommended. The variables 9minute, #home and 2kg are invalid. Blank spaces are not allowed in variable names. The variables my var and your car are invalid. Blank spaces are not allowed in variable names. The variables my var and your car are invalid.

62. MS Sadia Ejaz CIIT ATTOCK Rules for Declaring Variables (contd.) Both upper and lower cases are allowed. A user- defined variable is conventionally written in lower case. The constants are conventionally written in upper case. Both upper and lower cases are allowed. A user- defined variable is conventionally written in lower case. The constants are conventionally written in upper case. Special symbols cannot be used as variable name. Special symbols cannot be used as variable name. Reserved word cannot be used as variable name. The names int, void and while are invalid variables. Reserved word cannot be used as variable name. The names int, void and while are invalid variables.

63. MS Sadia Ejaz CIIT ATTOCK Rules for Declaring Variables (contd.) A variable can be up to 31 characters long for many compiler. If a variable consists of more than 31 characters, only first 31 characters will be used. The remaining characters will be ignored. A variable can be up to 31 characters long for many compiler. If a variable consists of more than 31 characters, only first 31 characters will be used. The remaining characters will be ignored. A variable can be declared only for one data type. A variable can be declared only for one data type.

64. MS Sadia Ejaz CIIT ATTOCK Variable Initialization The process of assigning a value to a variable at the time of declaration is known as variable initialization. The process of assigning a value to a variable at the time of declaration is known as variable initialization. Syntax Syntax  Data typevariable _name =value;  e.g. intn=100;  int n= 100 ;

65. MS Sadia Ejaz CIIT ATTOCK Tokens A program statement consist of variable names, keywords, constant, operator etc, these elements of statement are called tokens e.g. int main(){ int x,y; x = 5; }

66. MS Sadia Ejaz CIIT ATTOCK Example simple program #include #include int main(){ int x; x = 5; cout << x; return 0; }