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UNIT 1INTRODUCTION TO

VISUAL PROGRAMMING AND VB

UNIT 1: INTRODUCTION TO VISUAL PROGRAMMING & VBF3005: VISUAL BASIC PROGRAMMING

At the end of this chapter, the students should be able to:

Explain what is Visual Programming Language (VPL)

Understand the history of VPL

Learn a type of VPL: Visual Basic (VB)

o Definition

o Usage

o History

o Advantages

o Concept

o Examples

o Program Structure

Objectives

1.1 What is Visual Programming Language (VPL)?

It is a programming language that uses visual techniques to illustrate the relationship between

data or the changes to the data.

Despite the fact that the visual communication in VPL is higher compared to the traditional

text-based programming, text is still being used in visual programming.

Text is used in:

o Documentation

o Naming objects that

differentiate elements of

the same type

o Writing program code

(event, method)

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Note:Visual Technique: Includes sketching,

pointing, and instant

demonstration of any

manipulation carried out

on an object directly.

Example:Visual objects with the addition and subtraction

functions that will receive 2 numbers as the input to

generate one output.

Diagram 1.1


1.2 History of VPL

Combination of graphic computer + programming language + user interface

Year Description

1963

Ivan Sutherland – Created the Sketchpad system using the TX-2 computer at MIT.

The best example of the first computer graphic application.

The system allows user to use lightpen to design 2D graphic such as circle, line and

other operation such as copy.

1965

William Sutherland – developed the simple visual data flow language.

Develop menu system that can create, debug and run DFD in an integrated visual

environment.

1975

David Canfield Smith – completed his PHD with the title “Pygmalion: A Creative

Programming Environment”.

His work became the starting point to researches until today.

Paradigm of icon-based programming exists due to Pygmalion.

Table 1.1

1.3 Introduction to one type of VPL: Visual Basic

High Level Programming Language – developed from a DOS version; BASIC.

Easy to learn and the code are English-like statements.

The programming language is Visual based and is based on event.

1.3.1 Definition

Visual Basic is derived from 2 words:

Visual & Basic

We will look at the meaning of each word and the meaning of both words when combined.

VISUAL

Is a method to design graphical user interface.

You don’t need to write lines of codes to display the position of your objects just click and

drag to place the object at a suitable position on the screen.

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Diagram 1.2: Example of a Graphical User Interface

BASIC

Based on the BASIC (Beginners All-Purpose Symbolic Instruction Code), a language that is

commonly used by most programmers compared to other traditional programming languages

(e.g. FORTRAN).

VISUAL BASIC

Evolved from the original BASIC language and now contains hundreds of statement,

functions and keywords. Visual Basic is also a method to create Graphic User Interface,

(GUI).

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CLSPRINT “You did it!”PRINT PRINT “You are now a programmer.”

You did it!

You are now a programmer.

Example of BASIC Program Output produced


Diagram 1.3: User Interface with VB code

1.3.2 What is the function of Visual Basic?

Enable programmers to build average-sized applications with suitable GUIs quickly.

Enable a quick application development or Rapid Application Development –RAD software.

Examples of programming languages with RAD feature: Borland Delphi, Borland C++

Builder, Microsoft J++, Microsoft Visual Basic, etc.

Diagram 1.4: Visual Basic Interface

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1.3.3 History of Visual Basic

Visual Basic evolved from BASIC (Beginners All-Purpose Symbolic Instruction Code).Year Description

1960s John Kemeny and Thomas Kurtz at Dartmouth College developed BASIC

to write simple program.

The usage was on multiple platforms.

The main aim: to help individual learn to write a program.

Late 1980s Many versions of BASIC were developed, including MS-BASIC and

QuickBASIC (Qbasic).

1991 Microsoft Corporation has developed Visual Basic as a Windows

application designed to assist programmers in developing other event-

driven Windows applications.

September

1998

The 6th Version of Visual Basic has been launched.

Table 1.2

Diagram 1.5: Founders of the BASIC programming language

1.3.4 Difference between QBASIC and Visual Basic

QBASIC Visual Basic

DOS based Windows based

Requires long lines of codes to create a program Programs are easily written because it involves

mouse clicks on-screen buttons and drag &

drop tools.

QBASIC is a translator, easy to be tested but it is

difficult to be distributed and to be protected

unless you have a separate compiler.

Visual Basic requires a compiler

It is impossible to create bigger program with

QBASIC because its memory can only retrieve

not more than 0.16MB data. It is hard to create

visual effect using this language.

Large sized program with visual effects can be

developed easily because the program

development uses Microsoft Windows

graphical user interface (GUI).

Table 1.3

6

Thomas Kurtz John G. Kemeny


1.3.5 Advantages of using Visual Basic

Component Advantage

Tools Enables the development of small application for individual users, large

organisations and internet applications.

Data Access Create front-end applications with database and server access. (E.g.

SQL Server)

Internet Support Easy to retrieve documents and applications via the Internet or Intranet.

Active X Technology Allow integration with different applications.

Example: Microsoft Word Processor, Microsoft Excel.

Table 1.4

1.4 Visual Basic Concept

It combines the facilities in Basic Language and visual interface in order to help you in

creating interface and code for an application easily.

It is built in the Windows environment and deals with objects.

1.4.1 Understanding the Event-Driven Model

In the traditional procedural applications, it is the application that controls all the codes to be

executed in its sequence.

In the process of execution, the first line of code is being read and based on the instructions

from each line of code, it will trigger the necessary procedures.

In an event-driven application, codes do not go through a fixed direction. Codes are activated

based on an event, triggered by user action through messages from the system or another

application or the local application.

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Diagram 1.6: Visual Basic Interface

Diagram 1.7: Example of an event, triggered when user clicks the command button, Done

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1.4.2 Objects

VB deals with objects, which refer to ‘things’. Examples of objects in VB are form, textbox

and command button.

Each object in VB has its own characteristics or attributes called properties. Examples of

properties in VB are Caption and BackColor.

Objects can also carry out some actions such as Hide and Show.

Each object in VB has a unique and meaningful name. Usually an object’s name will begin

with three-lettered prefix that signifies the type of the object.

Prefix Object Example

lbl Label lblName, lblTitle

frm Form frmCalculator

cmd Command Buttons cmdPress

txt TextBox txtNumber,txtAddress

Table 1.6

1.5 Example of Program

This is an example of a program that carries out 2 operations; addition and subtraction.

Diagram 1.8: Application Interface

Program Code

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‘Declare 2 variables of type integerDim num1 As Integer, num2 As Integer

‘Add two numbersPrivate Sub cmdAdd_Click()num1 = txtNum1.textnum2 = txtNum2.texttxtAdd.text = num1 + num2End Sub

‘Subtract two numbersPrivate Sub cmdSubtract_Click()num1 = txtNum1.textnum2 = txtNum2.texttxtAdd.text = num1- num2End Sub


1.5.1 Program Structure

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Private Sub Event for an object Variable declaration

Any VB statements

End Sub

Note Event for an object

o Events can occur through user actions

such as a mouse click or a key press,

through programmatic control, or

even as a result of another window's

actions, e.g. Command1_Click ()

Visual Basic program statement

o Comprise functions, methods,

comments and procedures.

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prowince.files.wordpress.com · Web viewUNIT 1: INTRODUCTION TO VISUAL PROGRAMMING & VB F3005: VISUAL BASIC PROGRAMMING Author nida Last modified by user Created Date 6/19/2006 3:43:00