al_put_pixel - Allegro 5 API

       Draw  a  single  pixel  on  the  target  bitmap.  This operation is slow on non-memory bitmaps.  Consider
       locking the bitmap if you are going to use this  function  multiple  times  on  the  same  bitmap.   This
       function is not affected by the transformations or the color blenders.

       al_put_pixel - Allegro 5 API

ALLEGRO_COLOR(3alleg5), al_get_pixel(3alleg5), al_put_blended_pixel(3alleg5), al_lock_bitmap(3alleg5)

Allegro reference manual                                                                   al_put_pixel(3alleg5)

              #include <allegro5/allegro.h>

              void al_put_pixel(int x, int y, ALLEGRO_COLOR color)