Basics
More Complex Examples
Basics with Visual
Basic 2008
Welcome to this tutorial. I have to say congratulations on choosing Visual Basic as your first programming language as it is easy to use for creating forms and controls. It also gives you a genuine Microsoft Windows approach. So lets start.
Data Types
No matter in what language we program we always have the same principles and basic instructions. Even though the actual coding and methods might differ a bit, we have some basics that always apply. Some of these basics are variables and constants. Programs use variants and constants to store information (data) in memory.
Constants
are used
to declare information that are constant and can not change again.
Constants are declared at modular level and can be used over and over again without having
to type the actual data or string again.
Example:
Public Const
Name
As
String = "John Peter Osborne"
In this example we declared a constant and called it
Name. In the constant
Name
we stored the string representation, "John Peter Osborne". Now every
time we want to refer to the name "John Peter Osborne" we can simply
type
Name
and the program will return the value stored in the constant
Name. Easy don't you think?
Variables
are used to store data that can change all the time through the program
and therefore the name Variable. Variables can be declared at almost any
level including classes, modules, and functions.
Example:
Dim
Total
As Integer = 12
In this example we declared an Integer called
Total
and stored the value 12 in it. Should you now refer to
Total
the program will return the value 12. Now can change the value and
declare that Total
= 24 and the program will return the value 24 every time you refer to
Total,
until you change it again.
When we declare constants
and variables as data types like "integer" in the example above, we have
to decide exactly what type of data we are going to store. Different
data types take up different memory bites and can slow your program
down. Inspect the data types in the following table to see what they are
used for.
| Visual Basic type | Common language runtime type structure | Nominal storage allocation | Value range |
| Boolean | Boolean | Depends on implementing platform | True or False |
| Byte | Byte | 1 byte | 0 through 255 (unsigned) |
| Char (single character) | Char | 2 bytes | 0 through 65535 (unsigned) |
| Date | DateTime | 8 bytes | 0:00:00 (midnight) on January 1, 0001 through 11:59:59 PM on December 31, 9999 |
| Decimal | Decimal | 16 bytes | 0 through
+/-79,228,162,514,264,337,593,543,950,335 (+/-7.9...E+28)
†
with no decimal point; 0 through
+/-7.9228162514264337593543950335 with 28 places to the right of
the decimal; smallest nonzero number is +/-0.0000000000000000000000000001 (+/-1E-28) † |
| Double (double-precision floating-point) | Double | 8 bytes | -1.79769313486231570E+308
through -4.94065645841246544E-324
†
for negative values; 4.94065645841246544E-324 through 1.79769313486231570E+308 † for positive values |
| Integer | Int32 | 4 bytes | -2,147,483,648 through 2,147,483,647 (signed) |
| Long (long integer) | Int64 | 8 bytes | -9,223,372,036,854,775,808 through 9,223,372,036,854,775,807 (9.2...E+18 †) (signed) |
| Object | Object (class) | 4 bytes on 32-bit platform
8 bytes on 64-bit platform |
Any type can be stored in a variable of type Object |
| SByte | SByte | 1 byte | -128 through 127 (signed) |
| Short (short integer) | Int16 | 2 bytes | -32,768 through 32,767 (signed) |
| Single (single-precision floating-point) | Single | 4 bytes | -3.4028235E+38 through
-1.401298E-45 †
for negative values; 1.401298E-45 through 3.4028235E+38 † for positive values |
| String (variable-length) | String (class) | Depends on implementing platform | 0 to approximately 2 billion Unicode characters |
| UInteger | UInt32 | 4 bytes | 0 through 4,294,967,295 (unsigned) |
| ULong | UInt64 | 8 bytes | 0 through 18,446,744,073,709,551,615 (1.8...E+19 †) (unsigned) |
| User-Defined (structure) | (inherits from ValueType) | Depends on implementing platform | Each member of the structure has a range determined by its data type and independent of the ranges of the other members |
| UShort | UInt16 | 2 bytes | 0 through 65,535 (unsigned) |
† In scientific notation, "E" refers to a power of 10. So 3.56E+2 signifies 3.56 x 102 or 356, and 3.56E-2 signifies 3.56 / 102 or 0.0356.
I know it might seem a bit much at
first glance, but don't worry we'll go through it step by step in this
tutorial. If you liked this article then
Please Thumb This Up with a short review -
Let's continue to the next page.
Email us at: info@pro2visual.com
|
Get
your Website Listed on our Free Link Banner Directory |
Moving a borderless form in vb.net
Link Progress Bar with Timer in vb.net
How to open a folder using the process control