Delphi Basics : While command

DelphiBasics

While
Keyword

Repeat statements whilst a continuation condition is met

keyword While(While Expression do Statement;

Description

The While keyword starts a control loop that is executed as long as the Expression is satisfied (returns True).

The loop is not executed at all if the expression is false at the start.

You need Begin or End markers if multiple statements are required in the loop.

It is used when it is important that the statements are at only executed when necessary.

Related commands

Begin		Keyword that starts a statement block
Boolean		Allows just True and False values
Do		Defines the start of some controlled action
End		Keyword that terminates statement blocks
For		Starts a loop that executes a finite number of times
Repeat		Repeat statements until a ternmination condition is met
Until		Ends a Repeat control loop

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Example code : Display integer squares until we reach 100

var
  num, sqrNum : Integer;

begin
  num := 1;
  sqrNum := num * num;

  // Display squares of integers until we reach 100 in value
  While sqrNum <= 100 do
  begin
    // Show the square of num
    ShowMessage(IntToStr(num)+' squared = '+IntToStr(sqrNum));

    // Increment the number
    Inc(num);

    // Square the number
    sqrNum := num * num;
  end;
end;

Show full unit code

  1 squared = 1
  2 squared = 4
  3 squared = 9
  4 squared = 16
  5 squared = 25
  6 squared = 36
  7 squared = 49
  8 squared = 64
  9 squared = 81
  10 squared = 100