create_sub_bitmap - Creates a memory sub bitmap. Allegro game programming library.

       Creates a sub-bitmap, ie. a bitmap sharing drawing memory with a pre-existing bitmap, but possibly with a
       different  size  and  clipping  settings. When creating a sub-bitmap of the mode-X screen, the x position
       must be a multiple of four. The sub-bitmap width and height can extend beyond the right and bottom  edges
       of the parent (they will be clipped), but the origin point must lie within the parent region.

       create_sub_bitmap - Creates a memory sub bitmap. Allegro game programming library.

       Returns  a pointer to the created sub bitmap, or NULL if the sub bitmap could not be created. Remember to
       free the sub bitmap before freeing the  parent  bitmap  to  avoid  memory  leaks  and  potential  crashes
       accessing memory which has been freed.

create_bitmap(3alleg4),   create_bitmap_ex(3alleg4),   destroy_bitmap(3alleg4),   is_sub_bitmap(3alleg4),
       clear_bitmap(3alleg4), clear_to_color(3alleg4), expat(3alleg4), exscroll(3alleg4), exswitch(3alleg4)

Allegro                                           version 4.4.3                       create_sub_bitmap(3alleg4)

#include<allegro.h>BITMAP*create_sub_bitmap(BITMAP*parent,intx,y,width,height);