There are many
types of data that we come across in our daily life. For example, we need to
handle data such as names, addresses, money, date, stock quotes, statistics and
more everyday. Similarly in Visual Basic, we have to deal with all sorts of
of data, some can be mathematically calculated while some are in the form of
text or other forms. VB divides data into different types so that it is easier
to manage when we need to write the code involving those data.
5.1 Visual Basic Data Types
Visual Basic classifies the information mentioned above into two major data types, they are the numeric data types and the non-numeric data types.
5.1.1 Numeric Data Types
5.1.2 Non-numeric Data Types
Nonnumeric data types are data that cannot be manipulated mathematically using standard arithmetic operators. The non-numeric data comprises text or string data types, the Date data types, the Boolean data types that store only two values (true or false), Object data type and Variant data type .They are summarized in Table 5.2
5.1.3 Suffixes for Literals
Literals are values that you assign to 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.
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:
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
Examples of valid and invalid variable names are displayed in Table 5.4
He&HisFather *& is not acceptable
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 Variable Name As Data Type
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.
Dim yourName as String * 10
yourName can holds no more than 10 Characters.
Constants are different from variables in the sense that their values do not change during the running of the program.
5.3.1 Declaring a Constant
The format to declare a constant is
Const Constant Name As Data Type = Value
Const Pi As Single=3.142
Const Temp As Single=37
Const Score As Single=100