To

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Back to Reserved words.

Keyword used to indicate the final value of the control value in a For loop, and that the loop is to increment the control variable by 1 on each loop. The value specified by TO should be greater than the initial value of the for loop.

For to do

var i : integer;
begin
 for i := 1 to 10000 do
   begin
     //...
   end;
end;

The for to allow to execute code repeatedly for a fixed number of times.

Basic example

var
  loopValue, startValue, endValue, resultValue: integer;
begin
  startValue := 10;
  endValue := 11;
  resultValue := 0;
  for loopValue := startValue to endValue do
    begin
      resultValue := loopValue + resultValue;
    end;
end;

The loop execute two times and variable resultValue value is 21.

Start and end value same

var
  loopValue, startValue, endValue, resultValue: integer;
begin
  startValue := 10;
  endValue := 10;
  resultValue := 0;
  for loopValue := startValue to endValue do
    begin
      resultValue := loopValue + resultValue;
    end;
end;

The loop execute one time and variable resultValue value is 10.

Start value bigger than end value

var
  loopValue, startNumber, endNumber, resultValue: integer;
begin
  startValue := 10;
  endValue := 9;
  resultValue := 0;
  for loopValue := startValue to endValue do
    begin
      resultValue := loopValue + resultValue;
    end;
end;

The loop execute none time and variable resultValue value is 0.

Note that the value of the "for loop variable" is undefined after a loop has completed or if a loop is not executed at all. However, if the loop was terminated prematurely with an exception or a break (or even a goto statement), the loop variable retains the value it had when the loop was exited.

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