Constants, Data Type Conversion, Visual Basic Built-in Functions

Constants are named storage locations in memory, the value of which does not change during program Execution. They remain the same throughout the program execution. When the user wants to use a value that never changes, a constant can be declared and created. The Const statement is used to create a constant. Constants can be declared in local, form, module or global scope and can be public or private as for variables. Constants can be declared as illustrated below.

Public Const gravityconstant As Single = 9.81

Predefined Visual Basic Constants

The predefined constants can be used anywhere in the code in place of the actual numeric values. This makes the code easier to read and write.   LEARN MORE >>>>>

User-Defined Data Types in Visual Basic 6

Variables of different data types when combined as a single variable to hold several related informations is called a User-Defined data type.

A Type statement is used to define a user-defined type in the General declaration section of a form or module. User-defined data types can only be private in form while in standard modules can be public or private. An example for a user defined data type to hold the product details is as given below.

Private Type ProductDetails

ProdID as String

ProdName as String

Price as Currency

End Type

The user defined data type can be declared with a variable using the Dim statement as in any other variable declaration statement. An array of these user-defined data types can also be declared. An example to consolidate these two features is given below.

Dim ElectronicGoods as ProductDetails ' One Record

Dim ElectronicGoods(10) as ProductDetails ' An array of 11 records

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Arrays in VB

An array is a consecutive group of memory locations that all have the same name and the same type. To refer to a particular location or element in the array, we specify the array name and the array element position number. The Individual elements of an array are identified using an index. Arrays have upper and lower bounds and the elements have to lie within those bounds.

Each index number in an array is allocated individual memory space and therefore users must evade declaring arrays of larger size than required. We can declare an array of any of the basic data types including variant, user-defined types and object variables. The individual elements of an array are all of the same data type.

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VB PROCEDURES

Visual Basic offers different types of procedures to execute small sections of coding in applications. Visual Basic programs can be broken into smaller logical components called Procedures. Procedures are useful for condensing repeated operations such as the frequently used calculations, text and control manipulation etc. The benefits of using procedures in programming are:
1. It is easier to debug a program a program with procedures, which breaks a program into discrete logical limits.
2. Procedures used in one program can act as building blocks for other programs with slight modifications.
3. A Procedure can be Sub, Function or Property Procedure.
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Visual Basic 6 Data Types

Visual Basic uses building blocks such as Variables, Data Types, Procedures, Functions and Control Structures in its programming environment. This section concentrates on the programming fundamentals of Visual Basic with the blocks specified.

Modules

Code in Visual Basic is stored in the form of modules. The three kind of modules are Form Modules, Standard Modules and Class Modules.A simple application may contain a single Form, and the code resides in that Form module itself. As the application grows, additional Forms are added and there may be a common code to be executed in several Forms. To avoid the duplication of code, a separate module containing a procedure is created that implements the common code. This is a standard Module.

Class module (.CLS filename extension) are LEARN MORE>>

Getting Started with VB 6

Visual Basic is initiated by using the Programs option > Microsoft Visual Basic 6.0 > Visual Basic 6.0. Clicking the Visual Basic icon, we can view a copyright screen enlisting the details of the license holder of the copy of Visual Basic 6.0. Then it opens in to a new screen as shown in figure 1 below, with the interface elements Such as MenuBar, ToolBar, The New Project dialog box. These elements permit the user to buid different types of Visual Basic applications.

The Integrated Development Environment

One of the most significant changes in Visual Basic 6.0 is the Integrated Development Environment (IDE). IDE is a term commonly used in the programming world to describe the interface and environment that we use to create our applications. It is called integrated because we can access virtually all of the development tools that we need from     LEARN MORE >>