Transcript Overview
An Overview of Visual Basic .NET
Overview-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
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Slightly more advanced programming languages are called assembly languages
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Assembly languages simplify the programmer’s job by allowing the programmer to use mnemonics in place of the 0s and 1s in the program
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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 Overview-An Overview of Visual Basic .NET
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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
Another OOP term, inheritance , refers to the fact that you can create one class from another class
Attributes and behaviors that are not hidden said to be exposed to the user are 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
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