Delphi Basics : Until command

DelphiBasics

Until
Keyword

Ends a Repeat control loop

keyword Until(Repeat
Statement1;
{Statement2;
...}
Until Expression

Description

The Until keyword ends a control loop that is always executed at least once, and which terminates when the Expression is satisfied (returns True).

There is no need for Begin or End markers - the Repeat and Until keywords serve that purpose.

It is used when it is important that the statements are at least executed once.

Notes

The last Statement need not have a ; terminator - it is entirely optional.

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
While		Repeat statements whilst a continuation condition is met

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Example code : Display integer squares until we reach or exceed 100

var
  num, sqrNum : Integer;

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

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

    // Increment the number
    Inc(num);

    // Square the number
    sqrNum := num * num;
  Until sqrNum > 100;
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