This holds the index of the room that the hero is presently in, or 0 when he's outside.

The possible room numbers are as follows:

Room	Description	Movable Object	Items
0	Outdoors / exterior / main map	-	Green key
1	Lowest hut, right hand side	-	Poison
2	Middle hut, left hand side (Hero's start room)	-	Stove
3	Middle hut, right hand side	-	-
4	Highest hut, left hand side	-	-
5	Highest hut, right hand side	-	-
6	(unused index)	-	-
7	Corridor	-	-
8	Corridor	-	-
9	"Crate"	Crate	Shovel
10	"Lockpick"	-	Lockpick
11	Commandant's office	-	Papers
12	Corridor	-	-
13	Corridor	-	-
14	Guard’s quarters 1	-	Torch
15	Guard’s quarters 2	-	Uniform, Yellow key
16	Corridor	-	-
17	Corridor	-	-
18	“Radio”	-	Radio
19	“Food”	-	Food
20	"Red Cross parcel"	-	From parcel: Purse, Wire snips, Bribe, Compass
21	Corridor	-	-
22	Corridor to solitary	-	Red key
23	Mess hall, right room	-	-
24	Solitary confinement	-	-
25	Mess hall, left room	-	-
26	(unused index)	-	-
27	(unused index)	-	-
28	Lowest hut, left hand side	Stove	-
29	Tunnel 2, start of	-	-
30	Tunnel 2	-	-
31	Tunnel 2	-	-
32	Tunnel 2	-	-
33	Tunnel 2	-	-
34	Tunnel 2, end of	-	-
35	Tunnel 2	-	-
36	Tunnel 2	-	-
37	Tunnel 1, start of	-	-
38	Tunnel 1	-	-
39	Tunnel 1	-	-
40	Tunnel 1	-	-
41	Tunnel 1	-	-
42	Tunnel 1	-	-
43	Tunnel 1	-	-
44	Tunnel 1	-	-
45	Tunnel 1	-	-
46	Tunnel 1	-	-
47	Tunnel 1	-	-
48	Tunnel 1, end of	-	-
49	Tunnel 1	-	-
50	Tunnel 1 (initially blocked)	-	-
51	Tunnel 2	-	-
52	Tunnel 2	-	-

This is the current door id. Bit 7 is the door_REVERSE flag.

Used by the routines at is_door_locked, door_handling, door_handling_interior and solitary.

This is a queue of pending message indexes. Each is a two-byte value. Terminated by a single message_QUEUE_END byte ($FF).

This is a decrementing counter. When it reaches zero it shows the next message.

This is an index into the message that we're displaying or wiping.

message_display uses this. If it's 128 then we call next_message. If it exceeds 128 then we call wipe_message. Otherwise we proceed with displaying the next character.

This is a pointer to the next available slot in the message queue.

This is a pointer to the next message character to be displayed.

This holds a position (type: pos_t OR tinypos_t, depending on the code). It is used all over the code either for scratch space or for argument passing.

The only user of this is touch which stashes a copy of A here.

These are used by the vischar and item plotting code.

This holds a position (type: tinypos_t). This is populated when a vischar or item is readied for plotting. It's then used to control the rendering of masks into the mask buffer.

guards_follow_suspicious_character also uses it as a scratch space.

This holds the current vischar's isometric projected map position.

This is set by setup_vischar_plotting. When set, the top bit causes the character to be drawn flipped horizontally.

This holds the hero's map position (type: tinypos_t). event_roll_call, for example, uses this to test that the hero is within the roll call area.

This is used when drawing tiles and is also used to decide whether to permit the map to scroll.

This is set to searchlight_STATE_SEARCHING ($FF) when the hero is being searched for. It's set to searchlight_STATE_CAUGHT ($1F) when the hero is caught in the searchlight. Otherwise it's set to ($00..$1E) when the hero has evaded the searchlight.

Used by the routines at nighttime, plot_sprites.

Value	Meaning
255	Searching
31	Caught the hero
0..30	Tracking the hero

This is a copy of the first byte of the current room definition. It indexes roomdef_dimensions allowing interior_bounds_check to perform a bounds check.

This is the count of object bounds (places where the hero cannot move to) held in roomdef_object_bounds.

This holds up to four object bounds (places where the hero cannot move to) copied from the current room definition.

This holds up to four interior doors indices.

Used by the routines at setup_doors, door_handling_interior, get_nearest_door.

This holds a count byte followed by up to seven mask structures for the current room definition.

Used by the routines at setup_room and render_mask_buffer.

The first byte is a count, followed by <count> mask_t's, with the following format:

Type	Bytes	Name	Meaning
Byte	1	index	An index into mask_pointers (the RLE mask data pointer)
bounds_t	5	bounds	Isometric projected bounds of the mask. Used for culling.
tinypos_t	3	pos	If a character is behind this point then the mask is enabled. ("Behind" here means when the character's x-coord is greater and y-coord is greater-or-equal).

Written to by setup_item_plotting but never read.

This is a copy of item_definition height.

Used by the routines at setup_item_plotting, item_visible.

The two items which the hero is holding. Each byte holds one item. Initialised to ($FF,$FF) meaning no item in either slot.

The current character index.

This counts $00..$FF then wraps around.

Read-only by main_loop, picking_lock, cutting_wire, action_wiresnips, action_lockpick.

Write/read-write by wave_morale_flag.

This is the state of the bell.

Value	Meaning
0	Ring indefinitely
255	Don't ring
N	Ring for N calls

Read-only by automatics.

Write/read-write by in_permitted_area, ring_bell, event_wake_up, event_go_to_roll_call, event_go_to_breakfast_time, event_breakfast_time, event_go_to_exercise_time, event_exercise_time, event_go_to_time_for_bed, searchlight_caught, solitary, guards_follow_suspicious_character, event_roll_call.

Read-only by plot_score.

Write/read-write by increase_score, reset_game.

This is the 'hero is at breakfast' flag.

Write/read-write by process_player_input, end_of_breakfast, hero_sit_sleep_common.

This is the 'red morale flag' flag.

Value	Meaning
0	The hero is in a permitted area
255	The hero is not in a permitted area

Read-only by automatics, guards_follow_suspicious_character.

Write/read-write by in_permitted_area.

This counts down while there are no input events. An input event will reset it to 31. When it reaches zero the CPU will assume control of the hero.

Read-only by touch, automatics, character_behaviour.

Write/read-write by check_morale, process_player_input, charevnt_hero_release, solitary.

This is the 'in solitary' flag. When set ($FF) it stops set_hero_route working, stops automatics from running, stops process_player_input from running and in_permitted_area too.

Read-only by process_player_input, in_permitted_area, set_hero_route, automatics.

Write/read-write by charevnt_solitary_ends, solitary.

This is the 'morale exhausted' flag. It inhibits user input when non-zero.

Set by check_morale.

Reset by reset_game.

Read-only by process_player_input.

Write/read-write by check_morale.

This is the hero's current morale level. It ranges from morale_MIN (0) to morale_MAX (112).

Read-only by check_morale, wave_morale_flag.

Write/read-write by increase_morale, decrease_morale, reset_game.

This is the game clock. It ranges from 0 to 139.

Read-only by in_permitted_area.

Write/read-write by dispatch_timed_event, reset_map_and_characters.

This flag is set when character_index is valid. In character_bed_state etc.: when non-zero, character_index is valid, otherwise IY points to a character_struct.

Read-only by charevnt_bed, charevnt_breakfast.

Write/read-write by set_route, spawn_character, move_character, automatics, set_route.

This is the 'hero in bed' flag.

Read-only by event_night_time,

Write/read-write by process_player_input, wake_up, hero_sit_sleep_common.

This is the currently-displayed morale. It lags behind the actual morale at morale while the flag drifts to its target level.

Write/read-write by wave_morale_flag.

This is a pointer to the screen address where the morale flag was most recently plotted.

Write/read-write by wave_morale_flag.

This is the address of a door (in locked_doors) in which bit 7 is cleared when successfully picked.

Read-only by picking_lock.

Write/read-write by action_lockpick.

This is the game time at which player control will be restored, e.g. when picking a lock or cutting though a wire fence.

Read-only by picking_lock, cutting_wire.

Write/read-write by action_wiresnips, action_lockpick.

Value	Meaning
0	Daytime
255	Night-time

Read-only by main_loop, choose_game_window_attributes.

Write/read-write by set_day_or_night, reset_map_and_characters.

This holds the current contents of the red cross parcel.

This is an index used only by move_map.

This is the game window's scroll offset. It's (0,0) when displaying interior rooms, but varies when the exterior is shown.

This is a copy of the game window's current attribute byte. Assigned by set_attribute_from_A and used by zoombox_draw_tile_1 to set the attribute of a zoombox border tile.

This is the current bribed character.

Set by bribe_found. Read by B05B, C97E and tr_pursue.

This is a pointer to some bytes to output as pseudo-random data.

Initially set to $9000. Wraps around after $90FF.

This is a countdown until any food item is discovered.

Used by automatics and target_reached.

Used by plot_game_window and wipe_game_window.

These are the user-defined keys. It's pairs of (port, key mask).

This is a stash location used by plot_static_tiles.

Value	Meaning
0	Horizontal
255	Vertical

This records which input device was chosen.

Value	Meaning
0	Keyboard
1	Kempston
2	Sinclair
3	Protek