Determine the height and width of the terminal, and store this information into variables for subsequent use.

4000 d5          push de
4001 e5          push hl
4002 cd 69 bb    call &bb69
4005 ed 53 20 40 ld (&4020),de
4009 22 22 40    ld (&4022),hl
400c e1          pop hl
400d d1          pop de
400e c9          ret