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Overview-An Overview of Visual Basic .NET 1 An Overview of Visual Basic .NET

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Page 1: Overview-An Overview of Visual Basic.NET1 An Overview of Visual Basic.NET

Overview-An Overview of Visual Basic .NET 1

An Overview of Visual Basic .NET

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Overview Objectives

This overview contains basic definitions and background information, including:

A brief history of programming languages

An introduction to the terminology used in object-oriented programming languages

A Visual Basic demonstration

Information on using the tutorials effectively

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A Brief History of Programming Languages

Computers still rely on human beings to give them directions

These directions are called programs, and the people who write the programs are called programmers

Just as human beings communicate with each other through the use of languages such as English, Spanish, Hindi, and Chinese, programmers use a variety of special languages, called programming languages, to communicate with the computer

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Machine Languages

Within a computer, data are represented by microscopic electronic switches that can be either off or on

The off switch is designated by a 0

The on switch is designated by a 1 Instructions written in 0s and 1s are called machine

language or machine code

Each type of machine has its own language

Machine languages represent the only way to communicate directly with the computer

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Assembly Languages

• Slightly more advanced programming languages are called assembly languages

• Assembly languages simplify the programmer’s job by allowing the programmer to use mnemonics in place of the 0s and 1s in the program

• Mnemonics are memory aids—in this case, alphabetic abbreviations for instructions

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Assembly Languages

For example, the mnemonic MOV is used to move data from one area of the computer’s memory to another

Programs written in an assembly language require an assembler

The assembler is also a program

It converts the assembly instructions into machine code—the 0s and 1s the computer can understand

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High-Level Languages

High-level languages

Allow the programmer to use instructions that more closely resemble the English language

Represent the next major development in programming languages

Programs written in a high-level language require either an interpreter or a compiler to convert the English-like instructions into the 0s and 1s the computer can understand

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High-Level Languages

Like assemblers, both interpreters and compilers are separate programs

An interpreter translates the high-level instructions into machine code, line by line, as the program is running

A compiler translates the entire program into machine code before running the program

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Procedure-Oriented High-Level Languages

In procedure-oriented high-level languages, the emphasis of a program is on how to accomplish a task

The programmer must instruct the computer every step of the way, from the start of the task to its completion

The programmer determines and controls the order in which the computer processes the instructions

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Procedure-Oriented High-Level Languages

Examples include: COBOL BASIC (Beginner’s All-Purpose Symbolic Instruction Code) C

Procedure-oriented high-level languages are a vast improvement over machine and assembly languages

Some of the procedure-oriented high-level languages—for example, the BASIC language—do not require a great amount of technical expertise to write simple programs

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The Introduction of Windows

Windows software provides an easy-to-use graphical user interface (GUI)

The GUI is common to all applications written for the Windows environment

Although the standard interface found in all Windows applications makes the user’s life much easier, it complicates the programmer’s life a great deal

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The Introduction of Windows

Programmers found themselves spending countless hours writing instructions to create the buttons, scroll bars, dialog boxes, and menus needed in all Windows applications

Tasks that used to take a few lines of program code now needed pages

Because programming Windows applications required a great amount of expertise, it appeared that the beginning of the Windows environment meant the end of the do-it-yourself, nonprofessional programmer

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Object-Oriented/Event-Driven High-Level Languages

The object-oriented/event-driven high-level languages simplified the task of programming applications for Windows

In object-oriented/event-driven languages, the emphasis of a program is on the objects included in the user interface (such as scroll bars and buttons) and the events (such as scrolling and clicking) that occur when those objects are used

The object-oriented method allows the programmer to use familiar objects to solve problems

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Object-Oriented/Event-Driven High-Level Languages

The ability to use objects that model things found in the real world makes problem solving much easier

Visual Basic .NET is an object-oriented/event-driven programming language that is easy enough for a nonprogrammer to use, yet sophisticated enough to be used by professional programmers

With Visual Basic it takes just a few clicks of the mouse to include standard Windows objects such as buttons, list boxes, scroll bars, and icons in your Windows application

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OOP Terminology

OOP is an acronym for object-oriented programming It means that you are using an object-oriented

language to create a program that contains one or more objects

OOD is an acronym for object-oriented design Like top-down design, which is used to plan

procedure-oriented programs, OOD is also a design methodology, but it is used to plan object-oriented programs

OOD divides a problem into one or more objects

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OOP Terminology

An object is anything that can be seen, touched, or used

The objects used in an object-oriented program can take on many different forms

Objects include menus, radio buttons, and buttons included in most Windows programs

An object also can represent something encountered in real life

Every object has attributes and behaviors

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Object

An Object: Is Anything that can be seen or touched Has attributes that describe it Has behaviors that the object can either

perform or have performed on it

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OOP Terminology

The attributes are the characteristics that describe the object

An object’s behaviors, on the other hand, are the operations (actions) that the object is capable of performing

A class is a pattern or blueprint used to create an object

Every object used in an object-oriented program comes from a class

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OOP Terminology

A class contains—or, in OOP terms, it encapsulates—all of the attributes and behaviors that describe the object the class creates

Objects created from a class are referred to as instances of the class, and are said to be “instantiated” from the class

Abstraction refers to the hiding of the internal details of an object from the user

Hiding the internal details helps prevent the user from making inadvertent changes to the object

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Inheritance

Allows you to create one class from another class

The new class is called the derived class The original class is called the base class

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OOP Terminology

Attributes and behaviors that are not hidden are said to be exposed to the user

Another OOP term, inheritance, refers to the fact that you can create one class from another class

The new class, called the derived class, inherits the attributes and behaviors of the original class, called the base class

Polymorphism is the object-oriented feature that allows the same instruction to be carried out differently depending on the object

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Monthly Payment Application

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Using the Tutorials Effectively

The tutorials in this book will help you learn about Microsoft Visual Basic .NET, the newest version of the Visual Basic programming language

At the end of Lesson C in each tutorial you will find one or more Debugging exercises

In programming, the term debugging refers to the process of finding and fixing any errors in a program

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Using the Tutorials Effectively

Hands-on at your computer Step-by-step approach Help? notes identify common problems and explain how to

get back on track Tip notes provide additional information about a procedure Each tutorial is divided into three lessons To review and reinforce a lesson’s concepts

Summary Questions Exercises