Programming: Loop Concept in Visual Basic

Many people find it difficult to understand the concept of Loop in programming, that's the more reason for this article being in simple words easy to comprehend.

Computers are incredibly good at repeating the same task over and
over very quickly.

One of the key functions of a programming
language such as Visual Basic is to make it easy for a developer to
program a computer to perform these repetitive tasks.
Visual Basic
provides a number of language structures that tell a program to
perform a task repeatedly, either a specific number of times, or until
certain conditions are met.

We will look at each of these in detail:

1. Creating a Visual Basic For Loop
2. Incrementing a For Loop by a Value Greater Than 1
3. Early Exit of a For Loop
4. Continuing a For Loop

1. Creating a Visual Basic For Loop

The Visual Basic For loop is ideal for situations where
a task needs to be performed a specific number of
times. For example, perhaps a value needs to be
added to a variable 100 times. A Visual Basic For
loop consists of a header, a code block and a next
statement. The header contains information about
how many times the loop is to be performed, the code
block contains the statements to be executed on each
iteration and the next statement sends the loop back
to the header to repeat. The syntax of a For loop is as
follows:

For counterVariable = fromValue To toValue
... VB Statements ...
Next counterVariable

The easiest way to gain an understanding of For
loops is to see an example. The following code
excerpt declares a variable to act as the loop counter
and then performs a loop 5 times, displaying the
value of the counter on each loop iteration:

Dim intCount As Integer
For intCount = 0 To 5
       MessageBox.Show("Counter is currently: " + CStr(intCount))
Next intCount

For loops can also be nested. In a nested For Loop, the inner loop is
executed for each iteration of the outer loop For example:

Dim intCount1, intCount2 As Integer
For intCount1 = 0 To 5
       For intCount2 = 0 To 10
              'VB code here
       Next intCount2
Next intCount1

2. Incrementing a For Loop by a Value Greater Than 1

By default Visual Basic increments the For counter variable by a value
of 1. This number can be increased using the Step keyword at the end
of the For header statement. For example, to increment the counter by
10:

Dim intCount As Integer
For intCount = 0 To 100 Step 10
       MessageBox.Show("Counter is currently: " + CStr(intCount))
Next intCount

In the above example, the increment value applied to the counter
variable is increased to 10.

3. Early Exit of a For Loop

It is often necessary to exit a For loop before it has completed the
specified number of loop iterations. This is achieved using the Visual
Basic Exit For statement. This is typically used in conjunction with a
conditional If statement. The Following code example causes the loop
to exit if the counter is equal to 3:

Dim intCount As Integer
For intCount = 0 To 5
       If intCount = 3 Then Exit For
       MessageBox.Show("Counter is currently: " + CStr(intCount))
Next intCount

4.Continuing a For Loop

The Exit For command causes the For loop to exit entirely. Another
option is to skip the remaining statements in a loop under certain
circumstances but to continue to loop. This is achieved using the
Continue For statement. The following example skips the code in the
body of the For statement if counter is 3, and continues the loop at
the next iteration:

Dim intCount As Integer
For intCount = 0 To 5
       If intCount = 3 Then Continue For
       MessageBox.Show("Counter is currently: " + CStr(intCount))
Next intCount

When the above example is executed, a MessageBox will appear for
each iteration of the loop except for when the intCount value is equal
to 3.

Hope it's now crystal clear? Wanna hear a Yes!