VB2010 Lesson 6- Managing Data
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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 etc everyday. Similarly in Visual Basic 2010, 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. VB2010 divides data into different types so that it is easier to manage when we need to write the code involving those data. 6.1 Visual Basic 2010 Data Types Visual Basic 2010 classifies the information mentioned above into two major data types, they are the numeric data types and the non-numeric data types. 6.1.1 Numeric Data Types Numeric data types are types of data that consist of numbers, which can be computed mathematically with various standard operators such as add, minus, multiply, divide and so on. Examples of numeric data types are your examination marks, your height, your weight, the number of students in a class, share values, price of goods, monthly bills, fees and etc. In Visual Basic 2010, numeric data are divided into 7 types, depending on the range of values they can store. Calculations that only involve round figures or data that don't need precision can use Integer or Long integer in the computation. Programs that require high precision calculation need to use Single and Double decision data types, they are also called floating point numbers. For currency calculation , you can use the currency data types. Lastly, if even more precision is requires to perform calculations that involve a many decimal points, we can use the decimal data types. These data types summarized in Table 6.1
6.1.2 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 6.2 Table 6.2: Nonnumeric Data Types
6.1.3 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 VB2010 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 6.3. Table 6.3
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." 6.2 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 VB2010, 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 2010, you have to follow a set of rules. 6.2.1 Variable Names The following are the rules when naming the variables in Visual Basic 2010
Examples of valid and invalid variable names are displayed in Table 6.4 Table 6.4
6.2.2 Declaring Variables In Visual Basic 2010, one needs to
declare the variables before using them by assigning names and data
types. If you fail to do so, the program will show an error. They
are normally declared in the general section of the codes' windows
using the Dim statement. Dim Variable Name As Data Type Example 6.1
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,............. 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 6.1 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 6.2: Dim yourName as String * 10 yourName can holds no more than 10 Characters. 6.2.3 Assigning Values to Variables After declaring various variables using the Dim statements, we can assign values to those variables. The general format of an assignment is Variable=Expression The variable can be a declared variable or a control property value. The expression could be a mathematical expression, a number, a string, a Boolean value (true or false) and etc. The following are some examples: firstNumber=100 6.3 Constants Constants are different from variables in the sense that their values do not change during the running of the program. 6.3.1 Declaring a Constant The format to declare a constant is Const Constant Name As Data Type = Value Example 6.3
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