Decoded: Rogue (1980) by Toy, Arnold, Wichman
DOS version (1983) by Mel Sibony and Jon Lane
Source file: MAIN.C
Beginner friendly, line-by-line code walkthrough by MaiZure

MAIN.C is the game entry point and contains the game loop

Original code:
https://britzl.github.io/roguearchive/

Original code with line numbers
http://www.maizure.org/projects/decoded-rogue/MAIN_linenum.txt




1     COMMENT
2     COMMENT
3     COMMENT
4     COMMENT
5     COMMENT
6     COMMENT
7     COMMENT
8     COMMENT
9     COMMENT
10    COMMENT
11    COMMENT
12    COMMENT
13    COMMENT
14    COMMENT
15    COMMENT
16    BLANK
17    Include main game header (rogue.h)
18    Include curses library header (curses.h)
19    BLANK
20    Unused macro. Returns true if input with hyphen or forward slash
21    Unused macro. Returns true if characters match 
22    BLANK
23    Global flag for black and white mode
24    Global flag to disable screen retrace check (no waiting, just go)
25    If we're logging...
26    Then declare integers for the log method
27    End log check
28    BLANK
29    COMMENT
30    COMMENT
31    COMMENT
32    Declares a global structure to hold a register collection
33    BLANK
34    COMMENT
35    COMMENT
36    COMMENT
37    COMMENT
38    BLANK
39    Declares and defines main() with the usual suspects
40    Argument 1 is the count of command line arguments
41    Argument 2 is a pointer to the argument vector

THE MAIN ENTRY POINT FOR ROGUE

42    BLOCK START - main, the entry point for Rogue
43    Declare local pointers to the current command line arg and the save file
44    Declare a local temporary register state
45    Declares a 4 byte variable used as a temporary DMA buffer  
46    Declares a 2 byte string length integer
47    BLANK
48    Sets our global register pointer to the local main register structure
49    Moves two bytes of DMA buffer to the 4th byte of I/O, (DMA controller)
50    Initializes the real time clock
51    Display the title screen pic
52    Allocate basic heap for game objects
53    BLANK
54    Loads the environment settings in "rogue.opt".
55    Write protects the drive the game disk is on, default drive B
56    COMMENT
57    COMMENT
58    COMMENT
59    COMMENT
60    COMMENT
61    If the screen environment variable is set to "bw"
62    Set the flag for black and white mode
63    If the screen option setting (in rogue.opt) is longer than 4 characters
64    And the first 4 characters include the string "fast"
65    Then assert the force immediate redraw flag (used in ZOOM.ASM)
66    Initializes the dungeon number to zero. This will be randomized later
67    If protected mode is set
68    Loop on decremented argument counter and verify protect setting
69    Otherwise..
70    Just loop on the decremented argument counter
71    End protection check
72    Increments the current argument pointer, initially skipping program name
73    If we detected a switch as the first character,
74    BLOCK START - Handling a switch
75    SWITCH on switch letter 
76    BLOCK START - Switch on command line argument
77    CASE argument is 'R' or 'r'
78    Set save file to default save (rogue.sav)
79    END CASE
80    CASE argument is 'S' or 's'
81    Initialize a curses window
82    Disable scoring
83    Set is_saved to true (flag for screen dump during boss key)
84    Clear score
85    Ends execution immediately with no message
86    END CASE
87    If logging is enabled...(it isn't)
88    CASE argument is 'l'
89    Set log writing to -1 (this is not used)
90    Fix eventual random seed to 100
91    END CASE
92    CASE argument is 'K' or 'k'
93    Set log reading to -1 (this is not used)
94    Fix random seed to 100
95    END CASE
96    End logging enabled
97    BLOCK END - Switch on command line arguments
98    BLOCK END - Handling a switch
99    Check if no save file has been define...
100   Set save file to the current argument
101   End loop on command line arguments
102   If no save file is defined (due to lack of helpful arguments)..new game!
103   Set save file to 0 (redundant code)
104   Initialize a curses window
105   If black and white flag has been asserted
106   Force black and white mode (set attribute table to monochrome)
107   If retrace checking hasn't been set...
108   Set retrace check to desired state (fast draw or not)
109   Display game credits screen
110   If random number seed hasn't been set
111   Randomize the seed
112   Set the seed
113   BLANK
114   BLANK
115   Set up player stats
116   Set up loot tables
117   Set up names
118   Set up color tables
119   Set up other tables
120   Set up wands
121   Set up everything else
122   Animate and clear screen
123   Create a new level
124   COMMENT
125   COMMENT
126   COMMENT
127   Initialize healing over time background function
128   Start countdown for monster wandering trigger
129   Initialize hunger background function
130   Initialize moving monsters
131   Print starting banner message
132   Play start animation
133   End set up for new game
134   Kick off the game loop! Saved game reference is passed in.
135   BLOCK END - main
136   BLANK
137   COMMENT
138   COMMENT
139   COMMENT
140   COMMENT
141   Defines endit with no arguments
142   BLOCK START - endit, abnormal program termination
143   End game with an exit message
144   BLOCK END - endit
145   BLANK
146   Defines a random number incrementing function
147   COMMENT
148   COMMENT
149   COMMENT
150   COMMENT
151   COMMENT
152   COMMENT
153   Defines
154   Defines ran with one argument
155   BLOCK START - ran, random number generator seed incrementation
156   Multuply seed by 125
157   Minus itself (get the remainder)
158   Return the new seed
159   BLOCK END - ran
160   BLANK
161   COMMENT
162   COMMENT
163   COMMENT
164   COMMENT
165   Defines rnd with one argument
166   Argument 1 is the upper bound of the randon number range
167   BLOCK START - rnd, returns a random number from a range
168   Returns a random integer below the input range. Return value is the
      modular ring of the unsigned masked number seed (31-bit)
169   BLOCK END - rnd
170   BLANK
171   COMMENT
172   COMMENT
173   COMMENT
174   COMMENT
175   Defines roll with 2 arguments
176   Arguments are the number of die and the number of sides
177   BLOCK START - roll, rolls a die using input die configuration
178   Declare a local integer for the die total
179   BLANK
180   For each die...
181   Add a random number between 1 and the number of sides to total
182   Returns die total
183   BLOCK END - roll
184   BLANK
185   COMMENT
186   COMMENT
187   COMMENT
188   COMMENT
189   COMMENT
190   Defines playit with two arguments
191   Argument 1 is the saved game to load
192   Argument 2 is the black and white mode flag

THE GAME LOOP (Actually it's one line -- #214)

193   BLOCK START - playit, the main game play loop: read input and execute
194   If there is a saved game to load...
195   Reference an external variable for the cursor state (on/off)
196   Declare two integers (dead code)
197   BLANK
198   Load the game state
199   If we're configued for black and white mode...
200   Then forces the color mode to BW, (see CURSES.C).
201   If screen retrace check isn't set...
202   Then initialize it to the most recent configuration value (do_force)
203   Initialize the default system config, screen size, interrupt override
204   Turn the cursor state to on
205   Turn the cursor itself on. The input is current state. (see CURSES.C)
206   End loading of saved game, but if no saved game was passed...
207   Set the last player x position to the current position.
208   Set the last player y position to the current position.
209   Update the room pointer to the hero's current room
210   End of game init
211   Check if ME is defined (dead code, it's not defined anywhere)
212   Sets a variable for a (presumably) debug user
213   End check for ME
214   Begin Loop while the game is still active
215   Check for user input
216   End the game
217   BLOCK END - playit
218   BLANK
219   COMMENT
220   COMMENT
221   COMMENT
222   COMMENT
223   Define quit with no arguments
224   BLOCK START - quit, graceful program exit
225   Declare two integers for x and y cursor positions
226   Declare single byte to hold player response
227   Declares a quit state flag
228   BLANK
229   COMMENT
230   COMMENT
231   COMMENT
232   COMMENT
233   If qstate is already true...
234   Leave game in a hurry without stats display
235   Set qstate to true
236   Save line tracking variable to top
237   Set cursor ox and oy to the current cursor position
238   Move the cursor to the top left (See ZOOM.ASM for how this works)
239   Clears the line
240   Moves the cursor back to the upper left
241   If the terse flag isn't set (output is not pruned)
242   Then print a string prefix to the screen.
243   Print a formatted quit query to the screen
244   Update the screen with the new text
245   Read in player input
246   If the player answered that they wanted to check
247   Check if this is the demo version (it's not)
248   Display the demo ending
249   Otherwise display the real ending
250   Clear the screen
251   Moves the cursor to the top left
252   Print the final amount of gold
253   Calculate the final score
254   Exit the game
255   Othterwise, the player didn't choose to quit yet
256   Move the cursor to the top left
257   Clear the line
258   Print out the current status
259   Move the cursor to the current position
260   Set the temporary position to 0
261   Set count to zero
262   End case for demo version
263   End case for quitting
264   Set quit state to false
265   BLOCK END - quit
266   BLANK
267   COMMENT
268   COMMENT
269   COMMENT
270   COMMENT
271   Declares and defines leave with no arguments
272   BLOCK START - leave, quick exit from game
273   Update the screen
274   Move the cursor to the last status line
275   Clear it
276   Move it to the second to last line
277   Clear it
278   Move it back to the start of the line
279   End the game with a message (DOS prompt resumes below final game screen)
280   BLOCK END - leave
281   BLANK
282   COMMENT
283   COMMENT
284   COMMENT
285   Declares and defines fatal with two arguments
286   Argument 1 is the message to output
287   Argument 2 is an argument plugged in to the text (similar to printf)
288   BLOCK START - fatal, end process with message
289   Closes the curses session
290   Prints the message and argument to the console
291   Ends program
292   BLOCK END - fatal
293   EOF˙