3-4: Data Types in Visual Basic

Up until this point we have been assigning values to object properties and writing expressions involving values with something close to abandon! The last example brought a stop to our sloppy approach, and we now have to take a step back to understand more carefully how values and data are used in a Visual Basic program. This task is complicated by the fact that Visual Basic attempts to do certain things for us if we are sloppy in our approach to data. In fact much of what we have already done relies on Visual Basic to "correct" our sloppiness, if you like.

You are aware from Chapter 2 and the earlier parts of this chapter that there are different types of data. You have used string or text data, integer numbers, and boolean (true/false) data. A more complete list is contained in Table 3-2.

Table 3-2: A partial list of primitive data types.

Data Type Name	Storage size	Range of values
Boolean	2 byte	True or False (1 or 0)
Byte	1 byte	integers in the range 0 to 255
Char	2 bytes	0 to 65,535 representing the Unicode character set
Date	8 bytes	time/date between 0:00:00 on 1/1/0001 to 23:59:59 on 12/31/9999
Double	8 bytes	a real number; precision is about 14 digits to the right of the decimal point
Integer	4 bytes	integers in the range -2,147,483,648 to 2,147,483,647
Long	8 bytes	very big!
Short	2 bytes	integers in the range -32,768 to 32,767
Single	4 bytes	a real number, i.e. a number with a decimal (fractional) part; precision is limited to about 6 digits to the right of the decimal point.
String	depends on platform	up to approximately 2 billion Unicode characters

Notice that the types Short, Integer and Long are all integers with the difference that the Long data type can represent values much larger than 2,147,483,647, and Short can only represent numbers with magnitude up to just 32,767!

Similarly Single and Double are both real number data types with the difference that Double can represent not only larger values but also more accurate values (i.e. more decimal figures)