Syntax T_ON
Location Timings (DIY Toolkit - Vol H)

This toolkit provides the QL with five independent stop-watches which can be used to make accurate timings (more accurate than using DATE).

The stop-watches are linked into the QL’s ‘polled list’ of small routines which are run every frame on the computer (1/50 second on a British QL, 1/60 on most foreign QLs). There is a slight disadvantage in using the polled interrupts in that they are sometimes disabled by machine code routines, for example when accessing microdrives and disks.

Because of this, these commands are not much for timing programs which depend heavily on external hardware. These stop-watches are however very useful for comparing the speed of various program routines without having to make thousands of loops in order to show any difference in speed.

This command enables all the stop-watches. This must be issued before T_START can be used.