INTRODUCTION TO VISUAL BASIC 6.0

Visual Basic 6 is an application development tool used in developing Client/Server applications. Before beginning with Visual Basic 6, let's have a look at the Client/Server architecture.

Client/Server Architecture

Client/Server is an architecture, which can be used by multiple users simultaneously. The system also offers advanced toots that can be used for data security, data integrity, and database administration.

Business conditions are implemented as functions and procedures.

The data is processed in the Front End but stored and served by the powerful Back End.'Client/Server programming is also called Distributed Application Processing and Co-operative Application Processing.

Client/Server has three components, each focussing on a specified job.

• A Database Server.
• A Client Application.
• A Network for connecting the first two components.

Database Server

The functions of the database are as follows.

1.Managing a Single table containing information among many concurrent users

2.Controlling database access and other security requirements.

3.Protecting database table information with backup and recovery features.

4.Enforcing global data Integrity rules across all client applications.

Client Application

1.Presenting an interface to the user so that the data in the table can be manipulated With ease.

2.Managing presentation logic, such as popup lists on a data entry form, bar graphs etc.

3.Validating the data keyed in by the user.

4.Requesting and receiving information to and from the database server.

Network

The network and communication software are the vehicles that transport the data between the client and the server in the system.

Introduction to Visual Basic 6

The "Visual" part refers to the method used to create the graphical user interface (GUI). Rather than writing numerous lines of code to describe the appearance and location of interface elements. you simply add prebuilt objects into place on screen. If you've ever used a drawing program such as Paint,you already have most of the skills necessary to create an effective user interface.

The "Basic" part refers to the BASIC (Beginners All-Purpose Symbolic Instruction Code) language,a language used by more programmers than any other language in the history of computing Visual Basic has evolved from the original BASIC language and now contains several hundred statements, functions and keywords, many of which relate directly to the Windows GUI. Beginners can create useful applications by learning just a few of the keywords, yet the power of the language allows professionals to accomplish anything that can be accomplished using any other Windows programming language.

The Visual Basic programming language is not unique to Visual Basic. The Visual Basic Programming system, Applications Edition included in Microsoft Excel, Microsoft Access, and many other windows applications uses the same language. The Visual Basic Scripting Edition (VB Script) is a widely used scripting language and a subset of the Visual Basic language. The investment you make in learning Visual Basic will carry over to these other areas.

• User Interface : Visual Basic 6 is an application development tool developed from the BASIC language.BASIC language is a widely used language that provides a simple syntax. As the name suggests, a Visual Basic application is developed visually.you can develop graphical user interface using existing objects without writing numerous lines of code.

• Data Access : The data access options of Visual Basic allow you to create databases and applications for various database formats such as Microsoft SQL Server.

• Application Development :

• Using Visual Basic: 6, you can create event — driven applications. In a Visual Basic application, code is executed in response to events. This is different from a procedural application in which the code is executed according to a specific path defined by thé logic of the application.

• Another application development feature of Visual Basic is the powerful set of built-in controls that are provided for creating Windows-based applications, for example, Command button, Check box. These controls provide user interface without requiring complex programming. 

• You can also use dynamic-link library routines in applications. A DLL is a set of procedures that are external to an application, and can be called from within the application when required. They are linked to the application at run-time, as they not bound to the executable file. Visual Basic can use routines from Windows operating system SDK.

• ActiveX components help you in using reusing the code in applications.

• Visual Basic also provides a Setup Wizard, which 'is used to prepare an application for distribution. 

• Internet Oriented : Visual Basic 6 lets you develop Internet-aware applications.

Your finished application is a true.exe file that uses a Visual Basic Virtual Machine that you can freely distribute.

Hardware Requirements

Visual Basic 6.0 for windows requires at least Microsoft 95 / Windows NT 3.51 ,486 processor and a minimum of 16 MB of RAM. A complete installation of the most powerful version of Visual Basic 6.0 , enterprise edition, requires more than 250 MB of hard disk space.