This is a demonstration of a simple periodic task.

$ TYPE PERIODIC.ADA

with CALENDAR ; use CALENDAR ;
with TEXT_IO ; use TEXT_IO ;

procedure MAIN is

  task GO_PERIOD is
    entry START ;
  end GO_PERIOD ;

  task body GO_PERIOD is
    INTERVAL : constant DURATION := 1.0 ;  -- seconds
    NEXT_TIME : TIME := CLOCK ;  -- now

    procedure PERIODIC is
    begin
      PUT_LINE ( " IN PERIODIC " ) ;
    end PERIODIC ;
  begin
    accept START ;
    for I in 1 .. 10 loop  -- would never terminate with just "loop"
      delay NEXT_TIME - CLOCK ;  -- CLOCK is function in CALENDAR
      PERIODIC ;  -- call procedure
      NEXT_TIME := NEXT_TIME + INTERVAL ;
    end loop ;
  end GO_PERIOD ;
begin
  PUT_LINE ( " IN MAIN" ) ;
  GO_PERIOD.START ;  -- kick off the process

-- do something in "parallel" with PERIODIC
  PUT_LINE ( " still in MAIN" ) ;
  PUT_LINE ( " still in MAIN" ) ;
  PUT_LINE ( " still in MAIN" ) ;
  PUT_LINE ( " still in MAIN" ) ;
  PUT_LINE ( " still in MAIN" ) ;
  PUT_LINE ( " last of MAIN" ) ;
end MAIN ;

$ ADA PERIODIC
$ ACS LINK MAIN
$ RUN MAIN
 IN MAIN
 IN PERIODIC 
 still in MAIN
 still in MAIN
 still in MAIN
 still in MAIN
 still in MAIN
 last of MAIN
 IN PERIODIC 
 IN PERIODIC 
 IN PERIODIC 
 IN PERIODIC 
 IN PERIODIC 
 IN PERIODIC 
 IN PERIODIC 
 IN PERIODIC 
 IN PERIODIC 



This is the output from an old version of AdaEd

 IN MAIN 
 still in MAIN 
 still in MAIN 
 still in MAIN 
 still in MAIN 
 IN PERIODIC 
 still in MAIN 
 last of MAIN 
 IN PERIODIC 
 IN PERIODIC 
 IN PERIODIC 
 IN PERIODIC 
 IN PERIODIC 
 IN PERIODIC 
 IN PERIODIC 
 IN PERIODIC 
 IN PERIODIC 

  Execution time: 43 seconds
$ exit