1. An Overview of Object-Oriented Programming and C++1
An Overview of Object-Oriented Programming and C++
Object-Oriented Programming Using C++
Second Edition

2. 1 Objectives In this chapter, you will learn:
About the task of programming
About programming universals
About procedural programming
About object-oriented programming
About the C++ programming environment
How to create a main() function

3. 1 Objectives In this chapter, you will learn:
How to work with variables and the const qualifier
How to create comments
How to use libraries and preprocessor directives
How to use cout and cin
How to work with classes

4. The Task of Programming1
The Task of Programming
Programming a computer involves writing instructions that enable a computer to carry out a single task or a group of tasks
A computer programming language requires learning both vocabulary and syntax
Programmers use many different programming languages, including BASIC, Pascal, COBOL, RPG, and C++
The rules of any language make up its syntax
Machine language is the language that computers can understand; it consists of 1s and 0s

5. The Task of Programming1
The Task of Programming
A translator (called either a compiler or an interpreter) checks your program for syntax errors
A logical error occurs when you use a statement that, although syntactically correct, doesn’t do what you intended
You run a program by issuing a command to execute the program statements
You test a program by using sample data to determine whether the program results are correct

6. Programming Universals1
Programming Universals
All programming languages provide methods for directing output to a desired object, such as a monitor screen, printer or file
Similarly, all programming languages provide methods for sending input into the computer program so that it can be manipulated
In addition, all programming languages provide for naming locations in computer memory
These locations commonly are called variables (or attributes)

7. Programming Universals1
Programming Universals
Ideally, variables have meaningful names, although no programming language actually requires that they meet this standard
A variable may have only one value at a time, but it is the ability of memory variables to change in value that makes computers and programming worthwhile
In many computer programming languages, including C++, variables must be explicitly declared, or given a data type as well as a name, before they can be used

8. Programming Universals1
Programming Universals
The type determines what kind of values may be stored in a variable
Most computer languages allow at least two types: one for numbers and one for characters
Numeric variables hold values like 13 or -6
Character variables hold values like ‘A’ or ‘&’
Many languages include even more specialized types, such as integer (for storing whole numbers) or floating point (for storing numbers with decimal places)

9. Procedural Programming1
Procedural Programming
Procedural programs consist of a series of steps or procedures that take place one after the other
The programmer determines the exact conditions under which a procedure takes place, how often it takes place, and when the program stops
Programmers write procedural programs in many programming languages, such as COBOL, BASIC, FORTRAN, and RPG
You can also write procedural programs in C++

10. Early Procedural Programs1
Early Procedural Programs
When programming languages were first used, the programmer’s job was to break a task into small, specific steps
Each step was then coded in an appropriate language
Three basic control structures are used in procedural programming
In the first structure, a sequence, program steps execute one after another, without interruption

11. Early Procedural Programs1
Early Procedural Programs
Procedural programs also can include a second control structure called selection, which you use to perform different tasks based on a condition

12. Early Procedural Programs1
Early Procedural Programs
The third control structure used in computer programs is the loop
some programmers call the loop structure a repetition or iteration structure

13. Adding a Loop to a Simple Procedural Billing Program1
Adding a Loop to a Simple Procedural Billing Program

14. Modularity and Abstraction1
Modularity and Abstraction
Programming in the oldest procedural languages had two major disadvantages:
The programming process involved so much detail that the programmer (and any person reading the program) lost sight of the big picture
Similar statements required in various parts of the program had to be rewritten in more than one place
Writing programs became easier when programming languages began to allow the programmer to write methods
Using methods allows programmers to group statements together into modules or routines

15. Modularity and Abstraction1
Modularity and Abstraction

16. The Procedural Billing Program Containing Several Module Calls1
The Procedural Billing Program Containing Several Module Calls

17. 1
Encapsulation
Modules or procedures act somewhat like relatively autonomous mini-programs
Not only can modular routines contain their own sets of instructions, but most programming languages allow them to contain their own variables as well
The variables and instructions within a module are hidden and contained —that is encapsulated—which helps to make the module independent of all other modules, and therefore reusable

18. Object-Oriented Programming1
Object-Oriented Programming
Object-oriented programming requires a different way of thinking and adds several new concepts to programming;
You analyze the objects with which you are working— both the attributes of those objects and the tasks that need to be performed with and on those objects
You pass messages to objects, requesting the objects to take action
The same message works differently when applied to the various objects

19. Object-Oriented Programming1
Object-Oriented Programming
A method can work appropriately with different types of data it receives, without the need for separate method names
Objects can share or inherit traits of previously created objects, thereby reducing the time it takes to create new objects
Information hiding is more complete than in procedural programs

20. Object-Oriented Programming1
Object-Oriented Programming
The basic principles behind using object- oriented programming techniques involve:
Objects
Classes
Inheritance
Polymorphism

21. 1 Objects and Classes An object is any thing
A class consists of a category of things
An object is a specific item that belongs to a class; it is called an instance of a class
A class defines the characteristics of its objects and the methods that can be applied to its objects
It is conventional, but not required, to begin object names with a lowercase letter, and to begin class names with an uppercase letter

22. 1
Inheritance
The concept of using classes provides a useful way to organize objects; it is especially useful because classes are reusable or extensible
You can create new classes that extend or are descendants of existing classes
The descendent classes can inherit all the attributes of the original (or parent) class, or they can override inappropriate attributes

23. 1
Polymorphism
Programming modules might occasionally need to change the way they operate depending on the context
Object-oriented programs use polymorphism to carry out the same operation in a manner customized to the object
Without polymorphism you would have to use a separate module or method name for a method that multiplies two numbers and one that multiplies three numbers
Without polymorphism you would have to create separate module names for a method that cleans a Dish object, one that cleans a Car object, and one that cleans a Baby object

24. Getting Started in the C++ Programming Environment1
Getting Started in the C++ Programming Environment
Depending on your C++ installation, you can access the compiler by clicking an icon, selecting from a menu, or typing a command
The main work area in any C++ programming environment is the editor
An editor is a simplified version of a word processor in which you type your program statements, or source code
After you enter the source code for a program, you must compile the program

25. Getting Started in the C++ Programming Environment1
Getting Started in the C++ Programming Environment
When you compile, the code you have written is transformed into machine language—the language that the computer can understand
The output from the compilation is object code
When a C++ program is compiled, a file is created that has the same filename as the source code, but has the extension .obj
A runnable, or executable, program needs the object code as well as code from any outside sources (other files) to which it refers

26. Getting Started in the C++ Programming Environment1
Getting Started in the C++ Programming Environment
The process of integrating these outside references is called linking
An executable file contains the same filename as the source code and the object code, but carries the extension .exe to distinguish it as a program
When you compile a C++ program, error messages and/or warnings might appear
A C++ program with errors will not execute; you must eliminate all error messages before you can run the program

27. Creating a main( ) Function1
Creating a main( ) Function
C++ programs consist of modules called functions
Every statement within every C++ program is contained in a function
Every function consists of two parts:
A function header is the initial line of code in a C++ which always has three parts:
Return type of the function
Name of the function
Types and names of any variables enclosed in parentheses, and which the function receives
A function body

28. Creating a main( ) Function1
Creating a main( ) Function
A C++ program may contain many functions, but every C++ program contains at least one function, and that function is called main( )
If the main function does not pass values to other programs or receives values from outside the program, then main( ) receives and returns a void type
The body of every function in a C++ program is contained in curly braces, also known as curly brackets

29. Creating a main( ) Function1
Creating a main( ) Function
Every complete C++ statement ends with a semicolon
Often several statements must be grouped together, as when several statements must occur in a loop
In such a case, the statements have their own set of opening and closing braces within the main braces, forming a block

30. Working with Variables1
Working with Variables
In C++, you must name and give a type to variables (sometimes called identifiers) before you can use them
Names of C++ variables can include letters, numbers, and underscores, but must begin with a letter or underscore
No spaces or other special characters are allowed within a C++ variable name
Every programming language contains a few vocabulary words, or keywords, that you need in order to use the language

31. 1
Common C++ Keywords

32. Working with Variables1
Working with Variables
A C++ keyword cannot be used as a variable name
Each named variable must have a type
C++ supports three simple types:
Integer — Floating point — Character
An integer is a whole number, either positive or negative
An integer value may be stored in an integer variable declared with the keyword int
You can also declare an integer variable using short int and long int

33. Working with Variables1
Working with Variables
Real or floating-point numbers are numbers that include decimal positions, such as 98.6, , and -3.85
They may be stored in variables with type float, double, and long double
Characters may be stored in variables declared with the keyword char
A character may hold any single symbol in the ASCII character set
Often it contains a letter of the alphabet, but it could include a space, digit, punctuation mark, arithmetic symbol, or other special symbol

34. Working with Variables1
Working with Variables
In C++, a character value is always expressed in single quotes, such as ‘A’ or ‘&’
To declare a variable, you list its type and its name
In addition, a variable declaration is a C++ statement, so it must end with a semicolon
If you write a function that contains variables of diverse types, each variable must be declared in a statement of its own
If you want to declare two or more variables of the same type, you may declare them in the same statement

35. Working with Variables1
Working with Variables
Explicitly stating the value of a variable is called assignment, and is achieved with the assignment operator =
The variable finalScore is declared and assigned a value at the same time
Assigning a value to a variable upon creation is often referred to as initializing the variable

36. 1
The const Qualifier
A variable that does not change in a program should not be declared as a variable
Instead, it should be a constant
The statement const double MINIMUM_WAGE = 5.75; declares a constant named MINIMUM_WAGE that can be used like a variable, but cannot be changed during a program

37. 1
Creating Comments
Comments are statements that do not affect the compiling or running of a program
Comments are simply explanatory remarks that the programmer includes in a program to clarify what is taking place
These remarks are useful to later program users because they might help explain the intent of a particular statement or the purpose of the entire program
C++ supports both line comments and block comments

38. 1
Creating Comments
A line comment begins with two slashes (//) and continues to the end of the line on which it is placed
A block comment begins with a single slash and an asterisk (/*) and ends with an asterisk and a slash (*/); it might be contained on a single line or continued across many lines

39. Using Libraries and Preprocessor Directives1
Using Libraries and Preprocessor Directives
Header files are files that contain predefined values and routines, such as squrt( )
Their filenames usually end in .h
In order for your C++ program to use these predefined routines, you must include a preprocessor directive, a statement that tells the compiler what to do before compiling the program
In C++, all preprocessor directives begin with a pound sign (#), which is also called an octothorp
The #include preprocessor directive tells the compiler to include a file as part of the finished product

40. 1 C++ Output C++ provides several objects for producing output
The simplest object is called cout, pronounced “see out”
When contained in a complete C++ program, the statement cout<<“Hi there”; places the phrase “Hi there” on the monitor

41. 1
C++ Output
To indicate a newline character, you can use the escape sequence \n
Another way to advance output to a new line is to use the end line manipulator endl
Inserting endl into the output stream causes a new line plus all waiting output to become visible, a process called flushing the buffer
To create a program that declares two variables, assigns values to them, and creates output, perform the steps on pages 21 to 23 of the textbook

42. Program Listing for Output1.cpp

43. 1
Output of Output1.cpp

44. 1 C++ Input Many programs rely on input from a user
These are called interactive programs because the user interacts with the program statements
You create prompts by using the cout object; you retrieve user responses by using the cin object
The cin (pronounced see in) object fetches values from the keyboard
It is used with the extraction operator >>
Prior to a cin statement, it is almost always necessary to provide the user with a prompt, or a short explanation of what is expected

45. 1
C++ Input
Whitespace consists of any number of spaces, tabs, and Enter characters
You will add prompts and interactive input to the Output1.cpp program by following the instructions shown on pages 24 and 25 of the textbook

46. 1
Output of Output2.cpp

47. C++ Classes and Objects1
C++ Classes and Objects
When you use data types like int, char, and double within a program, you are using the C++ built-in, primitive or scalar data types
A major feature of object-oriented languages is the ability to create your own new, complex data types
These new types are called classes
A class can contain many simpler data types within it, as well as any number of functions
The relationship between these components, or fields, is often called a has-a relationship

48. C++ Classes and Objects1
C++ Classes and Objects

49. 1
A Complete Class Definition and a main( ) Method that Uses a Class Object

50. C++ Classes and Objects1
C++ Classes and Objects
You will create a Student class, and then create a program that uses a Student class object using the procedures outlined on pages 27 and 28 of the textbook
Creating a class provides a means to group data fields together in a logical way

51. 1
Summary
Programming a computer involves learning the syntax of a computer programming language and resolving logical errors
All programming languages provide methods for input and output of variable values
You declare a variable by providing it with a name and a type
Procedural programs consist of a series of steps or procedures that take place one after the other
Object-oriented programming adds several new programming concepts including objects, classes, inheritance, and polymorphism

52. 1
Summary
You write a C++ program by typing source code into an editor and compiling the program
C++ modules are called functions, and each function contains a header and a body
C++ variables must be given a type and a name
Simple types include integer for whole numbers, double and float for floating-point values, and character for any character
Comments are non-executing program statements

53. 1 Summary C++ supports line comments and block comments
A preprocessor directive tells the compiler to do something, such as to include a header file, before compiling the program
The cout statement (along with an insertion operator) is used to display values
When you create a class, you create your own C++ data type, which is a complex type composed of simpler types