There are 11 data types in Visual Basic 6. These are Boolean, Byte, Currency, Date, Double, Integer, Long, Object, Single, String, and Variant. Each of these data types have their own purpose. I am describing here all data type:
The Boolean data type has only two states, True and False. These types of variables are stored as 16-bit (2 Byte) numbers, and are usually used for flags.
The Byte data type is an 8-bit variable which can store value from 0 to 255. This data type is very useful for storing binary data. It can also be very useful when sending/receiving byte values.
The Double data type is a 64-bit floating point number used when high accuracy is needed. These variables can range from -1.79769313486232e308 to -4.94065645841247e-324 for negative values and from 4.94065645841247e-324 to 1.79769313486232e308 for positive values.
The Integer data type is a 16-bit number which can range from -32768 to 32767. Integers should be used when you are working with values that can not contain fractional numbers.
The Long data type is a 32-bit number which can range from -2,147,483,648 to 2,147,483,647. Long variables can only contain non-fractional integer values. I myself use Long variables over Integers for increased performance. Most Win32 functions use this data type for this reason.
The Single data type is a 32-bit number ranging from -3.402823e38 to -1.401298e-45 for negative values and from 1.401298e-45 to 3.402823e38 for positive values. This data type is to use when you need fractional numbers within this range.
The String data type is usually used as a variable-length type of variable. A variable-length string can contain up to approximately 2 billion characters. Each character has a value ranging from 0 to 255 based on the ASCII character set. Strings are used when Text is involved.