Page Byte Address Length Description
127 0 7F00 96
Screen refresh buffer
Used by the routines at E9D5, EA80, F0BE, F100, F3A0 and FC57. Each byte of the screen refresh buffer (SRB) corresponds to a segment of 8 character squares on the screen, the leftmost of which will be at x=0, x=8, x=16 or x=24. Each bit set in an SRB byte corresponds to a character square in the segment that needs refreshing. Bit 7 corresponds to the leftmost character square in the segment, bit 0 to the rightmost character square.
Note that, owing to a quirk in the way the SRB-updating routine at E9D5 works, the first 16 bytes of the screen refresh buffer correspond not to any part of the screen, but to the four rows of the play area that are immediately above the currently visible portion of the play area. Therefore, the screen-updating routine at EA80 ignores those bytes and starts inspecting SRB bytes at 7F10 instead.
Note also that the routine at 6EC5 uses the first 16 bytes of the SRB as a temporary backup store for the submessage indicator and submessage addresses at 7F81, and the routine at FC6A uses the first 32 bytes of the SRB as a temporary store for the top row of attribute bytes when scrolling the screen up and down.
127 96 7F60 33
Message buffer
Used by the routine at 6EC5 to prepare a message before displaying it. Also used by the routines at F18E and F1BA as temporary storage for one of the character buffers in groups 0xD7-0xDD.
127 129 7F81 16
Submessage indicator and message addresses
Used by the routine at 6EC5.
127 145 7F91 1
Unused
127 146 7F92 5
Message 0x02: '{number}'
Used as a submessage of message 0x2A. This message is cleared by the routine at 76FA when Sam picks up a phone, and updated by the routine at 77D3 as Sam dials.
127 151 7F97 2
Phone table entry address
Used by the routines at 776F and 77A3. Holds either the address of the second byte of the entry in the phone message table at 6B4B or 6B72 that corresponds to the phone that Sam is calling (if the person on the other end has a message for him) or picking up a call from, or the address of the final byte of the phone table at 6B72 (if the person Sam's calling has no message to give); this address contains the number of the message corresponding to the name that Sam must give in order to receive the telephone message, or 0x00 if no name is required to receive the message, or 0xFF if the person Sam's calling will respond with message 0x2E (I DUNNO NO {name}).
127 153 7F99 1
Time that Sam last lifted a ringing telephone
Checked by the routine at 76DD and set by the routine at 76FA (to the value of the second byte of the the system variable FRAMES, which is incremented every 5.12s).
127 154 7F9A 1
ID of the telephone that Sam is calling
Checked by the routines at 7500 (using the event entry at 6044) and 772F, and updated by the routines at 71DD, 776F, 7A0C and F1E3.
127 155 7F9B 1
Telephone call status flags
Used by the routines at 75F6, 76FA, 776F, 77D3 and 7A0C.
Bit(s) Meaning if set
0 Unused
1 The telephone call is finished (disconnected)
2,3 Unused
4 A digit is being dialled
5 The destination telephone is ringing
6 Sam must give a name in response to 'WHO'S THERE?'
7 Sam has picked up a ringing telephone
127 156 7F9C 2
Score
Checked by the routine at F0BE, and updated by the routine at 6EB1.
127 158 7F9E 2
Bucks
Checked by the routines at 7B6A, 7B9A and F0BE, and updated by the routines at 6100 and 6E87.
127 160 7FA0 2
Time the last message was displayed
Used by the routine at 6EC5. Holds the two least significant bytes of the system variable FRAMES as they were when the last message was displayed.
127 162 7FA2 6
Blown fuse delay counters
When a fuse is blown, the corresponding delay counter here is initialised by the routine at 74AA. The delay counters are checked and decremented by the routine at F404.
127 168 7FA8 1
Icon panel status flags
Used as a temporary buffer by the routines at 73E4, 7425 and 7603. Each bit set here (by the routine at 7425 or 7603) corresponds to an icon that should be displayed in the panel.
Bit(s) Icon
7 Fuse/Budgie
6 Door/Hook
5 Light bulb
4 Telephone
0-3 Unused
127 169 7FA9 1
Main loop task timer
Decremented and checked on every pass through the main loop by the routine at F000, and also checked by the routine at F144.
127 170 7FAA 10
Door knock status flags
Used by the routines at F2A8, F748 and F7CD. The bits in each byte here are used as follows:
Bit(s) Meaning if set
7 Somebody has just knocked on the door
6 Somebody is going to answer the door
0-5 Unused
127 180 7FB4 1
Blown fuse indicator
Used by the routine at F1FC, which stores a non-zero value here if any fuses are currently blown.
127 181 7FB5 1
Unused
127 182 7FB6 1
Fuse flags
Used by the routines at 74AA and 75A4. A bit set here indicates that the corresponding fuse has already been blown once. Bits 6 and 7 are unused.
Bit Fuse
0 No. 74
1 Hotel
2 No. 31
3 No. 19
4 No. 17
5 No. 15
127 183 7FB7 1
Index of the current message in the message queue
Used by the routines at 6EC5 and 75D0.
127 184 7FB8 8
Message queue
Used by the routines at 6EC5, 75D0 and FA79.
127 192 7FC0 4
Bullet buffer 1
Used by the routines at 621E, 65DB and 6670.
127 196 7FC4 4
Bullet buffer 2
Used by the routines at 621E, 65DB and 6670.
127 200 7FC8 1
Last value seen in the system variable FRAMES
Stores the value of the LSB of the system variable FRAMES as it stood at the end of the last pass through the main loop at F02B or the routine at 790D.
127 201 7FC9 1
Current disguise
Checked by the routines at 7222, 739D and 7500 (using the event entry at 605A), and changed by the routine at F95E. Holds the ID of Sam's current disguise.
ID Disguise
0 disguise0x1
1 disguise1x1
2 disguise2x1
3 disguise3x1
4 disguise4x1
5 disguise5x1
6 disguise6x1
7 disguise7x1
127 202 7FCA 6
Number string buffer
Used by the routine at 6E1A.
127 208 7FD0 2
Message 0x01: '{tens digit}/{name}'
Used as a submessage of messages 0x24, 0x28, 0x2E and 0x34. The message number of the name is inserted by the routine at 776F; the tens digit of the number of bucks is inserted by the routine at 7B6A or FB52.
127 210 7FD2 1
Message number to watch in the message queue
Set by the routines at 6100, 790D and 7996, and checked by the routine at 78FC.
127 211 7FD3 1
ID of the telephone Sam is holding
Set by the routine at 76FA and checked by the routine at 77D3.
127 212 7FD4 2
Time when the score was last incremented
Checked and set by the routine at 7AB6. Holds the value of the two least significant bytes of the system variable FRAMES as they were when the score was last incremented.
127 214 7FD6 5
Unused
127 219 7FDB 3
Location the police should head for when looking for Sam
Set by the routines at 71A0 and 7A39, and checked by the routine at 72B1.
127 222 7FDE 2
Random number seed
Used by the routine at F17F.
127 224 7FE0 7
Unused
Data is copied here from the game status buffer template at FFE0, but is never used.
127 231 7FE7 1
Bullet timer
Used by the routine at 65DB.
127 232 7FE8 1
Disguise status flags
Modified by the routine at 71AC, and checked by the routine at 7294. Each bit set here corresponds to a disguise that is known by the police. Bit 7 (corresponding to no disguise) is always set.
Bit Disguise
7 disguise0x1
6 disguise1x1
5 disguise2x1
4 disguise3x1
3 disguise4x1
2 disguise5x1
1 disguise6x1
0 disguise7x1
127 233 7FE9 1
Object inventory
Changed by the routine at 7603, and checked by the routines at 634C, 7500 (using the event entries at 60B0 and 60C6) and 7BE1. Each bit set here corresponds to an object in Sam's possession.
Bit(s) Object
0-5 Unused
6 Hook
7 Budgie
127 234 7FEA 1
Key inventory
Changed by the routines at 7603 and 7996, and checked by the routines at 7500 (using the event entries at 600A and 6097) and 7A39. Each bit set here corresponds to a key in Sam's possession.
Bit(s) Key
0-2 Unused
3 No. 74
4 No. 31
5 No. 27
6 No. 15
7 No. 19
127 235 7FEB 1
Police flags
Changed by the routines at 71DD, 7500 (using the event entry at 6097), 7A04, 7A39 and F731; checked by the routines at 73E4, 7B5C, 7B6A and 7CFE. The bits set here have the following meaning:
Bit(s) Meaning if set
0 Sam is wanted by the police
1-6 Unused
7 Sam is in jail
127 236 7FEC 2
High score
The high score is copied here from the game status buffer template at FFE0 by the routine at F8AE, but never used afterwards.
127 238 7FEE 1
Game mode indicator
Holds the current game mode (0-4). Checked by the routines at 7500 (using the event entry at 5FE0), 7996, 7AB6 and F080, and updated by the routine at F8AE.
Mode Meaning
0 Demo mode
1 The game has just started
2 Sam has entered no. 15 with the key
3 Sam has had the phone call about the key to no. 74 and gone to the top of the apartment building
4 The mob is after Sam
127 239 7FEF 1
Lives (first aid kits)
Used by the routines at 6592 and 7414. A first aid kit will be displayed in the icon panel for every bit that is set.
127 240 7FF0 10
Door status flags
Used by the routines at 76BC, F144, F293 and F2A8. In each flag byte here, bits 0-2 hold the door close delay timer (0 if the door is shut), and the set bit (if any) in bits 3-7 indicates the key that is required to unlock the door:
Bit Key
3 Key to no. 74
4 Key to no. 31
5 Key to no. 27
6 Key to no. 15
7 Key to no. 19
127 250 7FFA 1
Input device indicator
Set by the routine at 6177, and used by the routine at EAB2. Holds 0x6B ('k') if the Kempston joystick is being used, or 0x00 otherwise.
127 251 7FFB 1
Number of the character just moved (0xD7-0xE5)
Used by the routine at F1FC.
127 252 7FFC 1
Sam's status flags
Used by the routine at 74D8 to decide how to deal with Sam.
Bit Meaning if set Routine
0 Sam is being carried by a gangster or policeman 7AF4
1 Sam is immobilised (after meeting Lana) 6100
2 Unused
3 Sam is rolling or somersaulting 64CD
4 Sam is on the phone 77D3
5 Sam is blowing a fuse 75C2
Sam is switching a light on or off
Sam is raising or lowering a blind
Sam is throwing the hook
Sam is picking up an object
6 Sam is knocking on or opening a door F308
7 Sam is falling from the roof of a building FB93
127 253 7FFD 1
Last key pressed
Set by the main loop at F02B, and checked by the routine at ECE1. Holds the value from the keypress offset table corresponding to the last key pressed.
127 254 7FFE 1
x-coordinate of the leftmost column of the play area on screen
Checked by many routines, and modified by the routines at E80E and E845.
127 255 7FFF 1
y-coordinate of the topmost row of the play area on screen
Checked by many routines, and modified by the routines at E87C and E8B7.