Lesson 5: Managing Visual Basic Data

There are many types of data we come across in our daily life. For example, we need to handle data such as names, addresses, money, date, stock quotes, statistics and etc everyday. Similarly in Visual Basic, we are also going to deal with these kinds of data. However, to be more systematic, VB divides data into different types.

5.1 Types of Visual Basic Data

5.1.1 Numeric Data

Numeric data are data that consists of numbers, which can be computed mathematically with various standard operators such as add, minus, multiply, divide and so on. In Visual Basic, the numeric data are divided into 7 types, they are summarized in Table 5.1

Table 5.1: Numeric Data Types

5.1.2 Non-numeric Data Types

the nonnumeric data types are summarized in Table 5.2

Table 5.2: Nonnumeric Data Types 

5.1.3 Suffixes for Literals

Literals are values that you assign to a data. In some cases, we need to add a suffix behind a literal so that VB can handle the calculation more accurately. For example, we can use num=1.3089# for a Double type data. Some of the suffixes are displayed in Table 5.3.

Table 5.3

In addition, we need to enclose string literals within two quotations and date and time literals within two # sign. Strings can contain any characters, including numbers. The following are few examples:

memberName="Turban, John."
TelNumber="1800-900-888-777"
LastDay=#31-Dec-00#
ExpTime=#12:00 am#

5.2 Managing Variables

Variables are like mail boxes in the post office. The contents of the variables changes every now and then, just like the mail boxes. In term of VB, variables are areas allocated by the computer memory to hold data. Like the mail boxes, each variable must be given a name. To name a variable in Visual Basic, you have to follow a set of rules.

5.2.1 Variable Names

The following are the rules when naming the variables in Visual Basic

• It must be less than 255 characters
• No spacing is allowed
• It must not  begin with a number
• Period is not permitted

Examples of valid and invalid variable names are displayed in Table 5.4

Table 5.4

5.2.2 Declaring Variables

In Visual Basic, one needs to declare the variables before using them by assigning names and data types. They are normally declared in the general section of the codes' windows using the Dim statement.
The format  is as follows:

Dim variableNmae as DataType

Example 5.1

Dim password As String
Dim yourName As String
Dim firstnum As Integer
Dim secondnum As Integer
Dim total As Integer
Dim doDate As Date

You may also combine them in one line , separating each variable with a comma, as follows:

Dim password As String,  yourName As String, firstnum As Integer,.............

If data type is not specified, VB will automatically declare the variable as a Variant.
For string declaration, there are two possible formats, one for the variable-length string and another for the fixed-length string. For the variable-length string, just use the same format as example 5.1 above. However, for the fixed-length string, you have to use the format as shown below:

Dim VariableName as String * n, where n defines the number of characters the string can hold.

Example 5.2:

Dim yourName as String * 10

yourName can holds no more than 10 Characters.