al_start_timer - Allegro 5 API

       Start the timer specified.  From then, the timer’s counter will increment at a constant rate, and it will
       begin  generating  events.  Starting a timer that is already started does nothing.  Starting a timer that
       was stopped will reset the timer’s counter, effectively restarting the timer from the beginning.

       al_start_timer - Allegro 5 API

al_stop_timer(3alleg5), al_get_timer_started(3alleg5), al_resume_timer(3alleg5)

Allegro reference manual                                                                 al_start_timer(3alleg5)

              #include <allegro5/allegro.h>

              void al_start_timer(ALLEGRO_TIMER *timer)