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December 4, 2022 · View on GitHub

Visual Basic Newbie Tutorial : For...Next Loop (For Newbie)

Description

Hi VB newbie, do you know how to use for...next loop? If you don't, never mind. Read this tutorial to learn about that. You will learn how to use for...next loop by explanation and examples by me. Leave comments about this tutorial. Happy coding!

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Submitted On
By	Lam Ri Hui
Level	Beginner
User Rating	5.0 (10 globes from 2 users)
Compatibility	VB 3.0, VB 4.0 (16-bit), VB 4.0 (32-bit), VB 5.0, VB 6.0
Category	Coding Standards
World	Visual Basic
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Visual Basic Newbie Tutorial 1 : For...Next Loop

Loop
A loop is used to run a block of statements over and over. It is simply a group of commands that is repeated a specified number of times or for a specified length of time. An example of looping action : imagine you are sticking mail labels to several invitation cards. For each card, you check that the label matches the name on it, then you tick it off from your guest list, before pasting the mail label onto the card. You then proceed to the next card, repeat the check, tick and paste actions, and so on. This is essentially how a loop works.

There are two types of loops :
· Counter Loop - where repetition is based on a specified number of times
· Conditional Loop - where repetition is based on set conditions

Counter Loops
You use a counter loop when you want the computer to perform a task for a specific number of times. This is similar to running a track race of, say 12 laps. While running, you count the number of laps, and when you have completed 12, you stop.

A counter loop is also known as a For loop or a For/Next loop. This is because the ends of the loop are defined by the For statement and the Next statement. A For/Next loop requires two statements: the For statement at the beginning of the loop and the Next statement at the end of loop.

At the beginning of a For loop, you define a counter variable as well as the start and end values for the variable. For example, if you want the loop to repeat 12 times, you would set

For X = 1 To 12

The syntax of the loop is as follows

For countervariable = start To end
Statements to be executed
Next countervariable

The first time the loop is run, the counter variable is set to the value of the starting point (usually 1). After the statements are executed once, the counter variable reaches the Next statement where a counter registers a count of 1. The counter variable increase by one for each loop. Each time, the value in the counter is checked against the value of the end point. It stops when this value is reached.

Example

The following program will cause the computer to send out five beeps, one after another from the computer's speaker.

    For b = 1 To 5
        Beep
    Next b

The variable used is b. It stands for the first number in a For loop. Each time the loop is executed, the counter variable b increases by 1, until it reaches a value of 5.

Thus, the above code is same as following :

    Beep
    Beep
    Beep
    Beep
    Beep

Step Size
The default change in the loop counter is one. You can specify a different value for the change. This value is known as the step size. Referring to our example of track, if the track is 1000 meters long, a race of 10,000 meters will require 10 laps. On a track of 500 meters, it would require 20 laps. The step size changes the number of required laps or runs.

To change the step size, include step in the For loop. You can use any number, including decimals and negative numbers for the step size.

Example

Dim Count

    For Count = 0 To 100 Step 10
        Print Count
    Next Count

The output will as follow :

    0
    10
    20
    30
    40
    50
    60
    70
    80
    90
    100

Nested Loops
You can nest two or more For loops inside one another. Whenever you program needs to repeat a loop more than once, use a nested loop.

The following example shows two nested loops:

The inner loop is performed first. After it is completed, then the outer loop carries on.

Inner Loop
In the above example, the inner loop starts with the variable y = 1. It prints #. The semicolon will cause the next statement to print on the same line. Hence the second time the loop is carried out another # will be printed next to the first, resulting in ##. After the inner loop is repeated 5 times, the result will be #####.

Outer Loop
The outer loop begins with the variable x = 1. This will cause the inner loop to occur once, resulting in #####. The second time the outer loop occurs, another ##### will be printed, and so on. Thus after 3 repetitions of the outer loop the result will be

    #####
    #####
    #####

The Print statement by itself starts a new line for each row of #####, then include another Print Statement.

Dim x As Integer, y As Integer

For x = 1 To 3

        For y = 1 To 5
            Print "#";
        Next y

    Print
    Print
    Next x

Nested loops need not be hard to use. Just remember the rule : The inner loop must be completed before the Next statement for the outer loop is encountered. Use indentation and blank lines between loops to make them easy to read and debug.

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Visual Basic Newbie Tutorial 1 : For...Next Loop Ends Here
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