.org 100
.model flat		;this header is quite possibly fubar

mov ah, 0		;func 0h (set video mode)
mov al, 13		;mode 13h (320x200x256)
int 10			;ms-dos graphics

mov ax, 0		;func 0h (reset mouse)
int 33			;ms-dos mouse
mov ax, 20		;enable mouse driver
int 33
mov ax, 1		;func 1h (show mouse cursor)
int 33

mov ax, 0C		;func Ch (subroutine called on mouse click)
mov dx, [click]		;label to jump to on mouse click (im not sure about how to type that part ;)
mov cx, 8 		;user interrupt mask 0000 1000 (left button down)
int 33

loop:
jmp loop

click:

mov ah, 0		;func 0h (set video mode)
mov al, 1		;mode 1h (text 40x25)
int 10			;ms-dos graphics