A programming language and environment developed by Microsoft. Based on the BASIC language, Visual Basic was one of the first products to provide a graphical programming environment and a paint metaphor for developing user interfaces. Instead of worrying about syntax details, the Visual Basic programmer can add a substantial amount of code simply by dragging and dropping controls, such as buttons and dialog boxes, and then defining their appearance and behavior.

Although not a true object-oriented programming language in the strictest sense, Visual Basic nevertheless has an object-oriented philosophy. It is sometimes called an event-driven language because each object can react to different events such as a mouse click.

Since its launch in 1990, the Visual Basic approach has become the norm for programming languages. Now there are visual environments for many programming languages, including C, C++, Pascal, and Java. Visual Basic is sometimes called a Rapid Application Development (RAD) system because it enables programmers to quickly build prototype applications.

Application

An application is a collection of objects that work together to accomplish something useful. In VB the application is called a Project. A Project could be a the management of a Video store, the calculation of mortgages, a dating service or the Payroll for 1000 employees ...


Object

An object is a piece of software that has properties and functions that can be manipulated. Whew! You're here so, you must be somewhat familiar with the Windows environment. A window is an object. It has properties: size, color, position on the screen, etc. (The purists among you may want to talk about a class rather than an object but, at this point we just want to keep it simple, and the underlying concept is the same). The window has functions, also called methods, that can be manipulated: change the size, move it around, open it and close it. You do not have to write code to resize a window - you just click and drag. But somebody had to write code at some point. Fortunately for us, when they did they put it all in a nice little package and called it a window object. Now, whenever you need a window in your Project you can make a copy of the window object, change its properties for color or size very easily, and paste it where you want it. Then you can use its built-in methods to open it, close it when you want or resize it whenever necessary. When you create an application using objects and combining them to produce results, you are working in an object-oriented environment.


Event-driven

To produce an application in COBOL, a procedural language, you write COBOL source programs, you compile them into machine code and then you run them via a control interface such as JCL. A program can contain 1000's of lines of source code and could run for hours with no human intervention. In fact, in large installations, a jobstream can consist of a dozen programs, all automatically accepting input from the previous program and producing output for the next. The programmer can be blissfully unaware that the program has run unless something catastrophic happens.


In a VB project, the processes that occur have to be associated with events. An event is something that happens - the user clicks on a button, a form is opened, the result of a calculation is too large. The operation is event-driven because everything that executes does so as the result of some kind of event. The role of the programmer is to anticipate the events and to write the code that will be executed when the event occurs. A VB application is interactive in the sense that the user is constantly interacting with the program. The user inputs a Customer Id, the program checks the Id in the database and immediately brings up the customer's file or displays a message that the particular Id is invalid.