CST2601 Visual Basic I
Notes on For...Next Statement

For...Next Statement

Repeats a group of statements a specified number of times.

Syntax

For counter = start To end [Step step]
[statements]
[Exit For]
[statements]

Next [counter]

The For…Next statement syntax has these parts:

Part	Description
counter	Required. Numeric variable used as a loop counter. The variable can't be a Boolean or an array element.
start	Required. Initial value of counter.
end	Required. Final value of counter.
step	Optional. Amount counter is changed each time through the loop. If not specified, step defaults to one.
statements	Optional. One or more statements between For and Next that are executed the specified number of times.

Remarks

The step argument can be either positive or negative. The value of the step argument determines loop processing as follows:

Value	Loop executes if
Positive or 0	counter <= end
Negative	counter >= end

After all statements in the loop have executed, step is added to counter. At this point, either the statements in the loop execute again (based on the same test that caused the loop to execute initially), or the loop is exited and execution continues with the statement following the Next statement.

Tip Changing the value of counter while inside a loop can make it more difficult to read and debug your code.

Any number of Exit For statements may be placed anywhere in the loop as an alternate way to exit. Exit For is often used after evaluating of some condition, for example If...Then, and transfers control to the statement immediately following Next.

You can nest For...Next loops by placing one For...Next loop within another. Give each loop a unique variable name as its counter. The following construction is correct:

For I = 1 To 10
   For J = 1 To 10
      For K = 1 To 10
         ...
      Next K
   Next J
Next I

Note If you omit counter in a Next statement, execution continues as if counter is included. If a Next statement is encountered before its corresponding For statement, an error occurs.

For...Next Statement Example

This example uses the For...Next statement to create a string that contains 10 instances of the numbers 0 through 9, each string separated from the other by a single space. The outer loop uses a loop counter variable that is decremented each time through the loop.

Dim Words, Chars, MyString
For Words = 10 To 1 Step -1    ' Set up 10 repetitions.
   For Chars = 0 To 9   ' Set up 10 repetitions.
      MyString = MyString & Chars   ' Append number to string.
   Next Chars   ' Increment counter
   MyString = MyString & " "   ' Append a space.
Next Words