--- /dev/null
+/* %W% %G% %U% - (c) Copyright 1987, 1988 Chuck Simmons */
+
+/*
+ * Copyright (C) 1987, 1988 Chuck Simmons
+ *
+ * See the file COPYING, distributed with empire, for restriction
+ * and warranty information.
+ */
+
+C Empire Sources
+
+History
+
+ Apparently, this game was originally written outside of Digital,
+ probably at a university. The game was ported to DEC's VAX/VMS
+ from the TOPS-10/20 FORTRAN sources available around fall 1979.
+ Ed James got hold of the sources at Berkeley and converted
+ portions of the code to C, mostly to use curses for the screen
+ handling. He published his modified sources on the net in
+ December 1986. Because this game ran on VMS machines for so
+ long, a previous version is known as VMS Empire.
+
+ In early 1987 I reverse engineered the program and wrote a
+ version completely written in C. In doing this, I used lots
+ of structures and defined constants, and I attempted to make
+ the code flexible and easy to modify. The algorithms used
+ in this C version are completely new, the names of the commands
+ have been changed to be more mnemonic, and new commands have
+ been implemented. Only the format of the display is the same.
+ I suspect that many of my changes are slower and less
+ intelligently implemented than the originals. Also, I have
+ not implemented some of the original functionality.
+ However, my hope is that the commented C sources I have written
+ will prove far easier to modify and enhance than the original
+ FORTRAN sources. If you make changes for the better, by
+ all means send Ed James and I a copy.
+
+ The basic game has been heavily modified. I've changed the
+ types of objects built, modified the parameters on others,
+ and added lots of new kinds of movement functions. Read
+ the man page for a complete description.
+
+ The file 'bugs' contains lots of ideas for enhancements,
+ and describes the bugs I haven't been able to find.
+
+Organization
+
+ I have attempted to organize the sources into relatively few
+ coherent pieces. The pieces are:
+
+ empire.h -- definitions of data structures
+ extern.h -- definitions of global variables
+ data.c -- constant data
+ main.c -- option parsing
+ empire.c -- main program loop and outermost command handler
+ usermove.c -- move the user's pieces
+ compmove.c -- move the computer's pieces
+ edit.c -- handle the user's edit mode commands
+ game.c -- saving, restoring, and initializing the game board
+ display.c -- update the screen
+ term.c -- deal with information area of screen
+ math.c -- mathematical routines
+ object.c -- routines for manipulating objects
+ attack.c -- handle attacks between pieces
+ map.c -- find paths for moving pieces
+ util.c -- miscellaneous routines, especially I/O.
+
+Debugging notes
+
+ From command mode, there are two special commands that
+ can be used to turn debugging mode on or off. "++" turns
+ debugging mode on. "+-" turns debugging mode off.
+
+ When debugging mode is turned on, the following commands are
+ available:
+
+ "#" -- display a sector of the computer's map.
+
+ "%" -- enter "movie" mode. The computer continuously makes
+ moves, and the computer's map is shown on the screen.
+ This is useful for debugging the algorithm used by the
+ computer when it makes a move. Don't confuse this
+ with saving a movie and replaying it.
+
+ "@" -- enable/disable "trace pathmap" mode. If this command
+ is followed by a "+", trace pathmap mode is enabled.
+ If this command is followed by a "-", trace pathmap
+ mode is disabled. In this mode, every time a "pathmap"
+ is created, it is displayed. This is useful for
+ debugging the subroutines that search for an optimal
+ path along which to move a piece.
+
+ "$" -- enable/disable "print_debug". This command is also
+ followed by either a "+" or "-". In this mode,
+ various messages will be printed out at times which
+ may indicate that something is being done non-optimally.
+
+ "&" -- enable/disable "print_vmap". This command is followed
+ by a char that specifies the type of vmap to be
+ displayed. Values are
+
+ "a" -- army load maps
+ "l" -- transport load maps
+ "u" -- transport unload maps
+ "s" -- ship maps
+ "i" -- pruned explore map
+
+ Any other character disables the printing of vmaps.
+
+ The program will not provide any prompts for the debugging
+ commands. If you make a mistake, the computer just beeps.
+
+ You can also replay a saved movie with the normal "W" command
+ when debugging mode is turned on.
+
+ Also, the -DDEBUG flag can be turned on to cause consistency
+ checking to be performed frequently on the internal database.
+ This consistency checking is fairly exhaustive and checks for
+ all sorts of screwed up pointers. My measurements suggest
+ that consistency checking causes the program to run half
+ as fast.
+
+Final Notes
+
+ Unfortunately, I have a rather powerful mainframe at my
+ disposal which is somewhere between 10 and 40 times as
+ fast as a 68020 based computer. This means I can afford
+ to use extremely inefficient algorithms. I suspect that
+ running this program on a smaller machine, such as a Sun
+ workstation or Vax will not be overly rewarding. In particular,
+ the computer will take a very long time to move its pieces,
+ and it may not be desirable to save the game after every move.
+ (You mean your system doesn't write out 1/2 megabyte files in a
+ few milliseconds?) This second problem is easily fixed, but
+ I don't yet have any good ideas for fixing the first problem.
+
+ The size of a saved file can be easily tuned by reducing the
+ LIST_SIZE constant in empire.h. The only current simple tweak
+ for making the computer move faster is to reduce the size
+ of a map.
+
+Chuck Simmons
+amdahl!chuck
+
+Ed James
+edjames@ic.berkeley.edu
+ucbvax!edjames
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