Wasteland: the source

Current truth for this game. The workflow lives in kit/skills/; how this understanding developed lives in agent-history.md. Every fact names the routine or table it comes from. Unless marked live, a fact comes from reading the code in the snapshot named in orientation.md.

The game is in 64 parts (orientation.md, "The parts"): a resident engine, the programs loaded over it, nine tile sets and 42 maps. What is true of one part is in that part's own parts/<id>/facts.md, with that part's addresses. This file holds what spans the parts, and names the part beside every address it gives: "engine $25BD" is the engine's routine at $25BD.

Build

• The Electronic Arts release on two double-sided disks, four sides, with the boot files PRODOS and 2.0 on sides 1 and 3 and the game's data in raw sectors on all four (orientation.md, "The image").
• Written by Alan Pavlish: the start-up's bar reads "Start Utils Written by Alan Pavlish" (startup $81AD), and its packed text "Electronic Arts and Interplay Productions proudly present" and "Copyright 1986-88 Interplay Productions." (startup $84BE, $8505).
• The full credits are inside the game, as a poster in map 33: message 92 of its text block (map-33 $514F) reads "A computer software poster reads, "WASTELAND!"" and lists programming, design, maps, graphics, general help and playtest, 26 credits to 20 people, ending "Rated PG-13. Coming soon to a theatre near you." It is one of four messages on one wall square (column 20, row 25, class 11), each bump showing the next: 91 "Coming soon, "The Radheads!"", 92 the credits, 93 and 94 two more films, then 91 again (live). Map 1's message 26 is a gravestone: "Ken St. Andre, 4/28/47--4/28/87." (map-01 $4300), shown on the graveyard's square at column 27, row 24 (live). The string sweep of every program part and the decoded text of every text block (the 52 blocks' 4,920 messages, 478 the programs' and 4,442 the maps') find no other credit: the start-up's lines above are the only others that name a maker.
• Five people the poster credits are named elsewhere in the maps' text, each message shown by squares of its map as it loads (the squares' records, read with the Maps tab's port):
• map 13 message 70, on six wall squares: a wanted poster for Nishan Hossepian, "for crimes against computer software";
• map 33 message 27, at column 7, row 27: "Bill Dugan, Representative, Temple of Blood.";
• map 34 message 76, a wall at column 24, row 13: "Chalked on the wall: Dugan, B -- Rad overdose / Christensen, C -- Anthrax / Gonif, T -- Cirrhosis";
• map 38 message 90, a wall at column 1, row 12: a poster of a man typing at a computer, "STANCE THE GREAT MAP MAKER";
• and Ken St. Andre's gravestone, above.
• Side 3 holds an older build of the start-up at track 4, logical sector 16 (entry $7E06, against side 1's $7F2A; 2,766 of its 4,096 bytes differ), and its own boot sector, named "A JERKVISION PRODUCTION". Its credits read "Copyright 1986,87 Interplay Productions." where side 1's read "1986-88", and where side 1's start-up calls its title sounds, side 3's calls three RTS stubs ($7E03-$7E05) and writes no SID register. Booted, side 3 cannot run: its 2.0 loads side 3's track 34, logical sector 10 to $0200-$30FF, where side 1 has the engine and side 3 has other bytes, and the first raster interrupt after the hand-over goes through engine $04F9 into them and halts the processor on a JAM at $2931 (live). Run over side 1's engine instead, with side 3 in the drive, it shows a title picture it unpacks from side 3's track 3 and stops at "Computer defense initiative activated." (live, reference/side-3-start-up.png).
• Leftovers: three loads carry copies of other programs' bytes past the end of their own code, assembled for other addresses.
• The Ranger Center's $8600-$8FFF is the radio program's $7E00-$87FF, all 2,560 bytes.
• The radio's $874B-$87FF, and so also the Ranger Center's $8F4B-$8FFF, is the game's $874B-$87FF except two operand bytes ($87B4, $87B9), each 4 lower than the game's: a copy from a slightly different build of the game.
• The start-up's $860B-$86FF is the engine's $0A0B-$0AFF.

Memory layout

In play (parts/game/work/play-map.vsf), with $01 = $35: all RAM but the I/O area, both ROMs out.

The bitmap's 25th character row would be $7E00-$7F3F; with $D011 set to $37 (24 rows, startup $7F55-$7F57) it is hidden, except that screen_shake's random vertical scroll (engine $077A) brings its top lines into view for a moment, and the programs load from $7E00.

The disks and the loader

• Every read and write goes through the fast loader (engine $FF00), installed by the boot file. It moves whole 256-byte sectors with no link bytes: a file is a track, a logical sector and a page count, and logical sectors run down from there.
• Logical sectors map to physical ones by a table per speed zone: on tracks 1-17 logical n is physical 10*n* mod 21, on 18-24 8*n* mod 19, on 25-30 7*n* mod 18, on 31-35 6*n* mod 17 (engine $FFD3, $FDEA, $FDD8, $FFE8).
• After logical sector 0 the loader goes on to the track below, skipping track 18, at the logical sector the table at engine $C930 gives for that track (engine $FD0B). The table is laid out as if indexed by the track number less one, and is indexed by the track number: track 17 is entered at logical sector 0, track 24 at 17 and track 30 at 16, below their top sectors of 20, 18 and 17. Files are laid out on the disks by the same rule: maps 0, 2, 5, 11 and 19 cross one of those tracks, and each loads the sectors the rule names, not the ones a full track would give (the 42 maps loaded by the game's own enter_map compared with the image read both ways). The game writes through the same routine.
• Directories are on tracks 34 and 35, 64 four-byte entries a sector, the fourth byte the side that holds the file (engine $2790).
• File directories, track, logical sector, pages and side: maps T35/L14, item tables T35/L15.
• Stream directories, a start byte, a count of sectors from the base track and sector in the directory sector's last two bytes, a count of input pages and the side: modules T34/L16, map streams T35/L13, tile sets T35/L12, pictures T35/L10 (engine $2759).
• Every side carries every directory. A file stored on several sides is read from the side in the drive; one stored on one side is asked for by its number (engine $27C3).
• Packed streams are unpacked by code the engine loads over the third of the font's four pages, $C800 (glyphs $60-$7F, the lower case), from T35/L16 for each unpack and replaces from T35/L11 afterwards (engine $0524). T35/L11 holds the same 256 bytes as the third page of the font's own file, four pages from T34/L14 (engine $C800).
• A disk error prints "I/O ERROR" or "Write protected", then ". (RETURN)", on row 23, and RETURN, space or back-arrow retries; nothing gives up (engine $280C-$283E).

Play disks and the side check

• Each side's identity is the last three bytes of T35/L8: $D7 $CC side on the masters, $00 $CC side on copies (orientation.md, "The play disks").
• The side check (engine $1897) reads T35/L8 and wants its byte $FD to equal $ED, its byte $FE to be $CC and byte $FF the side asked for; until they are, it prints "INSERT SIDE n. (RETURN)". $ED is 0 in play, so the masters are refused (live). The start-up sets $ED to $D7 only around the check of side 1 before it loads the utilities (startup $81E4-$81ED), which is how Copy reads the masters.

Saving and the persistent world

• Each map is written back to its own sectors when the party leaves it (engine $2856, from $25BD); a map entered by a number from $80 up (the generic maps 5 and 11) never is (engine $2858).
• save_game (engine $18EA) copies zero page $02-$0F to $F478-$F485, sums $F400-$FBFF into one byte (engine $1918: for each page and Y = 0-254, the sum plus the byte, then plus Y and the carry out of that first addition; the carry out of the second is dropped, and byte 255 of each page is left out), keeps the sum at $F4FF, scrambles bytes 0-254 of every page by EOR with (2*Y* mod 256) EOR the sum (engine $1944), writes page n to T35, logical sector 7-n, and unscrambles. The key is the byte at $F4FF, saved in clear. The start-up reads the eight sectors back, unscrambles them and compares the sum (startup $830E-$832D), but a sum that does not match is accepted: every byte is EORed with twice its offset again, which leaves it as stored EORed with the key alone, and the start-up goes on with no message (startup $832F-$834C). So a save written in clear with a key of 0 loads as written, unless the sum the start-up forms from it comes out 0. Live: member 1's cash set to 12,345 in play and saved with S and Y; the eight sectors read off the disk image afterwards are this rule applied to memory as the save began, all 2,048 bytes, with the key $6B the sum as the code forms it.
• save_game has no side check, so a save lands on the side in the drive. It is called by Save (game $8820, after asking for side 1), by Radio (game $8802, before asking for side 1), at the end of every map change (engine $2600), by modules 1 and 3, by the Ranger Center's Start and by the utilities.

The maps

• A map in memory is two areas. From $3400: the class layer, a nibble a square, the high nibble for an even column (engine $0953); the number layer, a byte a square (engine $098E); then the map record, at $3A00 on a 32 x 32 map and at $4C00 on the four 64 x 64 maps, 0, 12, 22 and 26. From $DE00: the tile layer, a byte a square (engine $0B06), unpacked from the map's stream.
• The record begins with a $5C-byte header: address words for the packed text (engine $1E4F), the monster names and records (game $9E76, $9EA4), a list of records for each square class 0-15 (engine $09B8), the map's own routines (game $885C) and its non-player characters (game $A424); then the size (+$2C, engine $25D3), the chance of a random encounter after a step (+$2F, game $B017), the tile set (+$30, engine $25EE), the tile drawn off the map (+$33, engine $0B5E), what a step costs (+$34 and +$35, a fraction of a minute and minutes, and +$36, ticks of the elapsed count, game $AF32-$AF72), and 37 message numbers for the phrases of combat (+$37-$5B, game $BCE1, $BCE5).
• A square is a class and a number. When the party moves into it or arrives on it, its class's handler (game $ACF3, a table of 16 words) runs on the record that word number of the class's list names (engine $09B8): class 1 shows a message, 2 tests the party (skills, attributes, items, cash, party size), 3 and 15 are encounters, 4 shows another tile and a message, 5 is loot, 6 an action, 8 a question, 9 radiation, 10 an exit, 11 a wall that shows its message when walked into (game $915E), and 12 changes other squares. Classes 0, 7, 13 and 14 do nothing, and no map uses 7, 13 or 14.
• Radiation shows only at night: a class 9 square is drawn as tile 8, the radiation sign, from 18:00 to 05:59, and as its ground the rest of the day (engine $0B80-$0B8A; live). Tiles 0-8, the party, the creatures, the loot bag and the sign, are the same bytes in all nine tile sets as they load (the nine sets compared byte for byte); maps 0 and 26 exchange tile 7's bytes with the jeep's or the train's for their rides (map-00 $4FCD, map-26 $4EF9).
• Whether armour stops radiation depends on the square's message number. The radiation handler sets $A0, "ignore armour", to 1 (game $82E7), but the routine that applies the damage replaces it, for each member, with bit 0 of the square record's byte 0 (game $90AF-$90B4), which is the flag byte of the check squares it was written for and the message number of a radiation square. So armour counts on radiation squares whose message is even and not on those whose message is odd. The radiation records name messages 23 on map 0, 28, 29 and 30 on map 19, 69, 70 and 71 on map 20, 0 on map 26, 12 on map 31, and 43 and 0 on map 38 (live).
• Records change squares by pairs of class and number (engine $0A00). An action square's byte $80 + n loads module n to $CA00 and runs it; a smaller n calls the map's own routine n (game $8845).
• Nothing checks a list's word before it is used (engine $09B8). On map 11 the square at column 24, row 13, a wall on the screen, is class 2 number 2, and word 2 of class 2's list is $0000, so its record is read from address 0 on: the processor's port registers, then zero page. Its flags are the port's direction register, $2F, which has no checks tested and the move refused; the message it shows is the byte at $0001, the port, $35. So walking into that wall prints map 11's message 53, "Ah! Fresh air and open spaces once again.", every time (live). The wall is next to squares the party can walk to from the map's exit at column 28, row 0 (a search of the map's classes).

Text

• Every program has its own packed text block; the engine prints from the one $43/$44 points at (engine $1DFB). The engine's is $29E4-$30FE, messages 0-169, and $30FF is a spare byte.
• A block is a 60-byte alphabet, then a table of words, each the offset from the table to a group of four messages, then the groups. Codes are five bits, lowest bit first (engine $291D): code $1E capitalises the next letter, $1F adds $1E to the next code, and the code whose alphabet byte is 0 ends the message (engine $28F4).
• Control codes in the text (engine $1F42, $1F64): $0A singular or plural on the count $38, $0B the current character's name, $0C his or her, $0E him, her or it, $0F the count, $0D a new line, $05 and $06 wait for RETURN, space or back-arrow (wait_return, engine $2501).

Screen and controls

• The screen is a multicolour bitmap at $6000 with its colours at $5C00, in VIC bank $4000 (live: $DD00 = $86, $D018 = $79, $D011 = $B7, $D016 = $D8). The start-up writes $D011 as $37 (startup $7F55-$7F57, $7F91-$7F93); bit 7 reads back as the high bit of the raster line, which was past 255 when it was read. Text is drawn into the bitmap from the 6-pixel font at $C600 (engine $1F03).
• The one interrupt is the raster interrupt (engine $2947), which scans the keyboard; the NMI vector ends in an RTI, so RESTORE does nothing (engine $2966).
• Keys are read through the table at $C953: Apple II-style codes with bit 7 set, no shifted keys, no repeat, one new key per interrupt (engine $29BD-$29D4).
• Menus are a bar of words with hidden keys (engine $1B36, $1BBF): the game's bar is "Use Enc Order Disband View Save Radio", and its hidden keys I, J, K and L move the party, back-arrow and space (game $7F18).

Live tests

• Side 3 booted on its own; side 3's start-up run over side 1's engine ($7E00-$8DFF replaced at the hand-over, side 3 attached): above.
• The masters refused in play, the Copy utility's copies accepted (orientation.md, "The play disks").
• Space in play: $6A from 0 to 1 and the roster drawn over the bottom of the map window.
• I, J, K and L in play move the party north, west, south and east (party position $57/$58 before and after each key).
• The joystick: from play-map.vsf, a stick held on control port 2 for two seconds in each of the four directions and on fire, with checkpoints that do not stop on reads of CIA 1's port A ($DC00) and port B ($DC01) and, as the control, on the interrupt handler (engine $2947). The party stayed at column 55, row 62 ($57/$58), and in each hold port A was read 0 times against 203 or 204 reads of port B and as many interrupts; I then moved the party north, to row
• The same stick on port 1, whose lines are port B's, moved nothing either, but up brought up the first member's character sheet and fire turned it to the items page, as keys of the keyboard would.
• The click of a step: from play-map.vsf, L, L, K and J pressed with checkpoints that do not stop on step_done (game $AE26), play_sound_16 (engine $0741) and play_sound (engine $C993). The three steps the party took called each once; K, which the map refused, called none.
• The play screen captured with kit/c64/frame.py and drawn by site/lib/c64.js: 0 of 104,448 pixels differ from the emulator's picture, with the roster hidden and shown.
• Every map entered with the game's own enter_map, its pages, stream and tile set measured with two fills (orientation.md, "The maps").
• The save: member 1's cash set to 12,345 in play, S and Y pressed, the eight sectors of T35/L7-L0 read off the disk image afterwards and compared with the rule above applied to memory as the save began: all 2,048 bytes agree, key $6B.
• The credits poster: the party put north of map 33's poster wall with the game's own enter_map and K (south, into the wall) pressed five times, with RETURN through the credits' six screens; the messages came 91, 92, 93, 94, 91, and the clock did not move.
• The gravestone: the party put on map 1's grave at column 27, row 25 and I pressed; on the square north of it the game printed "The gravestone is inscribed: Ken St. Andre, 4/28/47--4/28/87."
• Map 11's wall with no record: the party put at column 23, row 13 with the game's own enter_map and L (east) pressed three times; each press printed message 53 and left the party, the square (class 2, number 2) and the clock as they were. The processor read $2F $35 at $0000-$0001 throughout.
• Radiation by the hour: the party put at column 57, row 38 of the world map and the view redrawn with the game's own redraw_view (game $AC8C) at 5:00, 6:00, 12:00, 17:00 and 18:00. The 36 radiation squares around the building at columns 57-58, rows 36-37 showed the sign at 5:00 and 18:00 and plain ground at the other three.
• The idle turn: play-map.vsf run for 3,000 frames with no key, with checkpoints that do not stop on the main loop (game $7E63), its idle turn (game $7E93) and, as the control, the interrupt handler (engine $2947): 2,999 interrupts, 58,486 passes of the loop (19.5 a frame), three idle turns, and the clock from 1:24 to 1:36, four minutes a turn on the world map. So with no key pressed a turn passes about every 840 frames, 17 seconds on a PAL machine.
• The main loop's pace: play-map.vsf run for 1,000 frames in chunks of 50, with the same checkpoints: 1,001 or 1,002 passes of the loop in every chunk (20.02 a frame) with $9F = $FF (no radiation in view), and 471 in the one chunk that held an idle turn. The port of the loop on the page makes 21.19 passes a frame on a processor that has every cycle; giving the video chip 1,075 cycles a frame brings it to 20.02, and the Geiger counter's player on the How it works page runs it so.
• The attribute roll: from the Ranger Center creating a character, SPACE rolled 32 attributes; each ended as a model of the broken exchange loop predicts, and 21 came out below the best three of their five dice (ranger $8382-$83C0; parts/ranger/facts.md).
• Radiation and armour: from play-map.vsf, every member's armour class set to 30 and CON to 200, the party stepped west onto the world map's radiation square at column 55, row 38 (record message 23, 5d6). With the message left at 23 the armour roll (game $A8C5) was skipped for all four members and they lost 22, 23, 16 and 14 CON; with it poked to 22 the roll was taken four times and nobody lost any.
• The dice in play: from the Ranger Center's attribute screen (play-create.vsf), SPACE pressed 125 times after random waits of 0.05 to 0.5 s; a checkpoint at ranger $8390 read the five dice of each of 1,000 attribute rolls: 1,043 ones, 869 twos, 786 threes, 727 fours, 749 fives and 826 sixes (even dice: 833 each), and two neighbours equal 699 times in 4,000. From play-map.vsf, a stub threw 4,096 pairs of dice with roll_2d6_open's instructions between them (engine $084A-$0850), each after the seed was moved 1 to 256 times as read_key moves it: 869 doubles, 21.2% (fair dice: 16.7%).
• Double experience for melee kills: from play-map.vsf, the party put in map 1's graveyard at column 27, row 25 with the game's own enter_map, every member's weapon cleared so that all four fought with fists, and K (south) pressed: "3 Shambler Ghouls appear at 14 feet." With every member ordered to attack each round, ten melee rounds (game $7F64) brought three kills. Each kill was worth 40 experience (engine $1C-$1E at game $8163), and each killer's experience went from 0 to 80 across the two adds at game $8163 and $8166. The screen named the kill ("KIT hammers the Shambler Ghoul for 6 points of damage killing it.") and printed no experience.
• The unlucky throw: from play-map.vsf, the same graveyard (map 1, column 27, row 25, enter_map), every weapon cleared, then Hell Razor (record $F500) given LK 3 (+$10) and a Throwing knife (item 15) in slot 1, equipped (+$BD, +$1F = 1); K brought "2 Shambler Ghouls appear at 14 feet." With every member ordered to attack, the first throw stopped at game $A7E7, where weapon_damage has written the roll into its two ADC operands ($A7EC, $A7F0): the roll was 10, and 2 and 0 were written there, the roll of a 1 and a 1. weapon_damage returned 65,535 ($A7F3: X:A = $FFFF), the kill path at game $A6E5 ran, and the screen read "Hell Razor attacks and hits 1 Shambler Ghoul for 65532 points of damage spinning it into a dance of death." (reference/unlucky-throw.png).
• Who can make that throw: the luck bonus is −3 for LK 3 or 4, −2 for 5 or 6 and −1 for 7 or 8 (game $A7C3); weapon_damage adds it to the roll with plain ADCs ($A7EA-$A7F0), while the melee path adds it through num2_add_clamped (engine $07C6), which stops at 0. Of the item table's thrown and fired weapons the Throwing knife has the fewest dice, 2 (item 15, byte 6); every other gun and rocket has 3 or more (the Mangler's and Sabot rocket's 2 × dice − armour is never fewer than their dice), and explosives take no luck ($A054). So only a 1 and a 1 on the knife with an LK of 3 or 4 goes below 0. No loot record of the 42 maps names item 15 or a random class-2 item (43 records, scanned with the levels page's port); Christina, NPC 1 of map 32 ($40AE), carries one in her slot 3. The ranger roll gives an LK of 3 or 4 for 261 of the 7,776 ways five dice fall (3.4%), the best three of five for 6. The highest hit-point seed of any named monster in the 42 maps is the Night Terror's, 32,000 (map 23, monster 1), which gives at most about 40,000 hit points (game $9483-$94B9).
• The pictures' pace: the title run from the start-up's play-title snapshot for 2,000 frames with no key, with checkpoints that do not stop on the animation tick (engine $05C5), the calls that pass its flags (engine $05DA) and the channels' step (engine $05E6), read every 50 frames. While the title's picture moved, the engine called the tick 3,508 to 3,553 times in 50 frames, every call passing the flags, and the channels stepped 7 times, about 7 steps a second; in a later stretch of the same sequence 2,624 to 3,176 calls and 5 or 6 steps. Between the two the flag at engine $AC was 0 and nothing moved.

Comment sample

• Before the audit: seed 1988 drew three comments from each of 21 strata out of the 11,532 line and side comments that the 64 parts' listings hold as their own (work/lead/sample.py): one stratum for each annotator's range, and one for the maps' descriptions that a decoder wrote, 7,973 comments (69%). Three agents that wrote none of the 63 checked them against the bytes: 48 were right, 14 had a wrong detail and 1 had the code wrong, so 15 of 63, 23.8% (Wilson 95% interval 15.0-35.6%). Weighted by the strata's sizes the rate was about 52%, because two of the three generated descriptions drawn carried an error of their template. The details were callers and paths left out, counts, the keys a prompt takes, and a field read alike for every value of a flag; the one wrong comment had taken an operand's value in the snapshot for a constant (map 49's poisoned needle, said to miss its target: the member comes from an operand the game writes when a Use begins). All 15 were rewritten to agree with the code.
• The audit: 22 agents that wrote none of the comments then checked all 11,532 against the bytes, the hand-written ones by range and the generated ones by template, and rewrote 2,441: 424 of the 3,559 hand-written comments and 2,017 of the 7,973 generated ones. Of those, 627 had the code wrong and the rest a detail. The generated descriptions' errors came from their templates: a check square's tests said to run when the party arrives, where with bit 7 of its flags clear they run on a move onto the square, and with bit 6 clear only on a Use; readers cited for a field they read only for some values of a flag; encounter ranges given without their unit (feet, ten to a square); exits said to lead to maps 128 and above, where the game loads map 5 or 11; the armour roll that bit 0 of a record's first byte decides left out; and map bytes that a BIT in the game or the engine addresses, said to be read by nothing, where the BIT runs and reads them, to no effect. The hand-written ones' were the sample's kinds. The lines of these facts files and of the pages that repeated such a claim were rewritten with them.
• After the audit: seed 6510 drew a second sample the same way, three from each of the 20 hand-written strata and 20 from the generated one, and four more agents that had written and audited none of it checked the 80: 77 were right, 3 had a wrong detail and none had the code wrong, 3.75% (Wilson 95% interval 1.3-10.5%). Of the hand-written comments 3 of 60 were wrong in a detail, 5.0% (1.7-13.7%); of the generated ones none of 20 (0-16.1%); weighted by the strata's sizes, 1.25%. The three: one of the game's three instructions that address a byte left out (death $7E0C); the skill list's header said to print on row 2, where the new line it opens with puts it on row 3 (module 2 $CC63); and play_sound's last write said to start the note, which sound 11's does not, its control byte $A4 having the gate bit clear (engine $C993). All three were rewritten, and so were five neighbouring comments of the death screen that left out the game's instructions in the same way.

Pokes that change the game within its own parameters. Each one names the variable it changes and whether it has been tested live. Untested pokes are labelled as candidates.