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Event Driven Programming

Objectives

After studying this unit, you will be able to:
• Understand the various data types and its variables
• Discuss the variables and its various declaration
• Explain the Dim statement
Introduction

Calculations and data storage is basic building block of any programming language. So it is very
important to understand them in Visual Basic. Although the calculations themselves are quite
simple , but there are some important issues to be understood along with them like how to store
data, what data types are allowed in Visual Basic, where and when to declare variables and
constants and most importantly the type compatibility among various data types.

4.1 Data Types

Data type determines type of data variable can store. In all programming languages, you define
a real-world data that refers to some specific type and needs to be understood by the compiler.
The compiler of the language defines the rules for different types of data that is to be allowed. This
type could be numeric, a string user defined or date. All compilers are CLS(Common Language
Specification) compliant i.e., it allows for certain data types. It enables cross-language program-
ming. This interoperability ensures that if you write an application in suppose Visual Basic and
the datatypes used are CLS compliant then any other language Framework can exchange informa-
tion with the application. A list of Visual Basic’s simple data types are given below:

1. Numeric
Byte Store integer values in the range of 0 - 255
Integer Store integer values in the range of (-32,768) - (+ 32,767)
Long Store integer values in the range of (- 2,147,483,468) - (+ 2,147,483,468)

Single Store floating point value in the range of (-3.4x10-38) - (+ 3.4x1038)
Double Store large floating value which exceeding the single data type value
Currency Store monetary values. It supports 4 digits to the right of decimal point
and 15 digits to the left

2. String
Use to store alphanumeric values. A variable length string can store approximately 4 billion
characters.

3. Date
Use to store date and time values. A variable declared as date type can store both date and time
values and it can store date values 01/01/0100 up to 12/31/9999.

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