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1. An Overview of Object-Oriented Programming and C++. Object-Oriented Programming Using C++ Second Edition. 1. Objectives. In this chapter, you will learn: About the task of programming About programming universals About procedural programming About object-oriented programming

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an overview of object oriented programming and c

1

An Overview of Object-Oriented Programming and C++

Object-Oriented Programming Using C++

Second Edition

objectives

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
objectives3

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
the task of programming

1

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
the task of programming5

1

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
programming universals

1

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)
programming universals7

1

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
programming universals8

1

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)
procedural programming

1

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++
early procedural programs

1

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
early procedural programs11

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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
early procedural programs12

1

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
modularity and abstraction

1

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
encapsulation

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
object oriented programming

1

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
object oriented programming19

1

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
object oriented programming20

1

Object-Oriented Programming
  • The basic principles behind using object-oriented programming techniques involve:
    • Objects
    • Classes
    • Inheritance
    • Polymorphism
objects and classes

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
inheritance

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
polymorphism

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
getting started in the c programming environment

1

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
getting started in the c programming environment25

1

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
getting started in the c programming environment26

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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
creating a main function

1

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
creating a main function28

1

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
creating a main function29

1

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
working with variables

1

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
working with variables32

1

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
working with variables33

1

Working with Variables
  • Real or floating-point numbers are numbers that include decimal positions, such as 98.6, 1000.00002, 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
working with variables34

1

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
working with variables35

1

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
the const qualifier

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
creating comments

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
creating comments38

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
using libraries and preprocessor directives

1

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
c output

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
c output41

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
c input

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
c input45

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
c classes and objects

1

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
c classes and objects50

1

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
summary

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
summary52

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
summary53

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