al_draw_pixel - Allegro 5 API

       Draws  a  single  pixel  at x, y.  This function, unlike al_put_pixel(3alleg5), does blending and, unlike
       al_put_blended_pixel(3alleg5),  respects  the  transformations  (that  is,  the   pixel’s   position   is
       transformed,  but  its  size  is  unaffected  - it remains a pixel).  This function can be slow if called
       often;  if  you  need  to  draw   a   lot   of   pixels   consider   using   al_draw_prim(3alleg5)   with
       ALLEGRO_PRIM_POINT_LIST from the primitives addon.

       • x - destination x

       • y - destination y

       • color - color of the pixel

         Note:  This function may not draw exactly where you expect it to.  See the pixel-precise output section
         on the primitives addon documentation for details on how to control exactly where the pixel is drawn.

       al_draw_pixel - Allegro 5 API

ALLEGRO_COLOR(3alleg5), al_put_pixel(3alleg5)

Allegro reference manual                                                                  al_draw_pixel(3alleg5)

              #include <allegro5/allegro.h>

              void al_draw_pixel(float x, float y, ALLEGRO_COLOR color)