While

while Bool_var loop
   --...--
   end loop;  

Loop_Name : while Bool_var loop
   --...--
   end loop Loop_Name; 

Index := 21;
While index in 1 .. 20
Loop
    Index := index + 1;
    End loop;

while True loop
  if Stop then exit; end if;
  End Loop;

Main:
while not stop_main loop
  get_input:
  while input /= "q" loop
    Get(input)
    if input = "Abort" then exit Main; 
    end if;
    End Loop get_input;
  End Loop Main;