D $BB57 This routine draws a bright green on black stippled border from (0,0) to (31,21)
C $BB57 Preserve registers.
C $BB5B Store the address of the first border UDG in CHARS for use in #R$DF0F.
C $BB61 Initialise loop counter to $14 for the 20 stippled squares in the vertical borders.  Register A holds the number of the UDG to draw at coords (C,B) which is (y,x).
C $BB63 Set up character 0 in A with coords of (0,E).
C $BB68 Preserve loop counter.
C $BB69 Draw next cell in the left-hand border, bottom to top.
C $BB70 Draw next cell in the right-hand border, bottom to top.
C $BB73 Restore loop counter.
C $BB75 Loop back until stippled vertical borders are complete.
C $BB77 Initialise loop counter for horizontal stippled squares between the borders.
C $BB79 Point at UDG for bottom stippled border.
C $BB7B Set vertical coordinate to 0.
C $BB7F Draw next cell in the bottom border, right to left.
C $BB84 Draw next cell for the top border, right to left.
C $BB89 Loop back for the rest of the cells in the top/bottom borders.
C $BB8D Point at UDG for top-left corner, set coord's to (0,0) and print.
C $BB95 Point at UDG for top-right corner, set coord's to (31,0) and print.
C $BB9C Point at UDG for bottom-left corner, set coord's to (0,21) and print.
C $BBA4 Point at UDG for bottom-right corner, set coord's to (31,21) and print.
C $BBAB Restore registers and return.

C $8A4E Display green border
C $91AD Display green border
C $94F0 Display green border
C $B8E2 Display green border
C $B93D Display green border
C $C11A Display green border
C $C3F0 Display green border

D $C2E3 This is a sound effect used in various places when changing the display (previously known as 'unknown69')