Tells if Allegro has to used fixed rate timers.
When running in clean DOS mode, the timer handler dynamically reprograms
the clock chip to generate interrupts at exactly the right times, which
gives an extremely high accuracy. Unfortunately, this constant speed
adjustment doesn't work under most multitasking systems (notably
Windows), so there is an alternative mode that just locks the hardware
timer interrupt to a speed of 200 ticks per second. This reduces the
accuracy of the timer (for instance, rest() will round the delay time to
the nearest 5 milliseconds), and prevents the vertical retrace simulator
from working, but on the plus side, it makes Allegro programs work under
Windows. This flag is set by allegro_init() if it detects the presence of
a multitasking OS, and enables the fixed rate timer mode.
The following projects include source code containing this keyword: