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                                Using Timers
 
Timers are typically used to let a program pause before processing user
input or to let a program carry out a task at a given time. Since timers for
Presentation Manager applications are provided through the message queue,
only non-Presentation Manager programs use the MS OS/2 timer functions.
 
Counting Synchronously
 
You can cause your program to pause for a given number of seconds by using
the DosSleep function. The DosSleep timer function waits the specified
number of milliseconds before returning control. The following code fragment
causes the program to pause for 60 seconds (60,000 milliseconds):
 
DosSleep(60000L);
 
DosSleep actually yields execution control to the system, so it is also a
convenient way to let other processes or threads execute while you pause.
This is useful if two processes (or two threads) need to synchronize their
execution. DosSleep yields control even if you specify zero milliseconds. As
long as the processes have equal priority, control does not return from
DosSleep until the other process has had an opportunity to execute.
 
Counting Asynchronously
 
If a program wants to carry out other tasks while the timer counts out the
interval, it can use the DosTimerAsync function. This function sets a timer
without stopping the program. When the interval elapses, the system clears a
given semaphore. The program must monitor the semaphore to determine when
the time has elapsed.
 
The following code fragment creates a system semaphore and then calls the
DosTimerAsync function to count an interval while the program performs other
activities:
 
DosCreateSem(CSEM_PUBLIC, &hSem, "\\sem\\abc.sem");
DosSemSet(hSem);
DosTimerAsync(5000L, hSem, &Timer);      /* start timer         */
    .
    .  /* other processing */
    .
DosSemWait(hSem, SEM_INDEFINITE_WAIT);  /* wait until timer     */
                                        /* clears the semaphore */
 
If the program wants the timer to count out the interval repeatedly, it can
use the DosTimerStart function. Unlike the DosTimerAsync function,
DosTimerStart does not stop after the first interval is counted. It repeats
the count and clears the semaphore each time the interval elapses.
 
A process can stop a timer by using the DosTimerStop function.
 
 
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