While statements specify the repeated execution of a statement sequence depending on the value of a Boolean expression. The expression is evaluated before each subsequent execution of the statement sequence. The repetition stops as soon as this evaluation yields the value FALSE.
WhileStatement = WHILE expression DO StatementSequence END.
WHILE j > 0 DO j:= j DIV 2; i:= i+1 END WHILE i#j DO IF 1 > j THEN i : = i-j ELSE j:= j-i END END WHILE (t # NIL) & (t^.key # i) DO t : = t^.left END