The files in this directory contain the C code for the builtin predicates
supported by the system.

To add a builtin to the system, follow the procedure outlined below:

I. Installing C code:

*	Go to the directory "sim/builtin".

*	Look at the #define's in file builtin.h and choose a number (between
	0 and 255) which is not in use, to be the new builtin number.  Let
	that number be N1.  Add to builtin.h the line: 

		#define   NEWBUILTIN   N1
	
*	The convention is that the code for the builtin will be in a 
	parameterless procedure named b_NEWBUILTIN. Modify the file
	sim/builtin/init_branch by adding the lines:

		extern int b_NEWBUILTIN();

		set_b_inst ( NEWBUILTIN, b_NEWBUILTIN);

	in the appropriate places.

*	The builtins are compiled together into one executable file,
	"builtin".  Update "Makefile" by appending the name of your object
	code file at the end of the line "OBJS = ..." and inserting the
	appropriate commands to compile your C source file, e.g.:
	
	    OBJS = [ ... other file names ... ] newbuiltin.o
	    
	    ...
	    
	    newbuiltin.o: $(HS)
	    	cc $(CFLAGS) newbuiltin.c

*	Execute the updated Makefile to create an updated executable
	file "builtin".

*	Go to the directory "sim" and execute Makefile to install the new
	file "builtin".

II. Installing Prolog code:

*	Assume that the builtin predicate to be added is "newbuiltin/4".
	
*	Go to the directory "lib/src" (where the Prolog source for the
	builtin and library routines is kept.)
	
*	Each builtin definition is of the form

		pred( ... ) :- '_$builtin'(N1).

	where N1 is an integer, the builtin number.
	
*	Create a Prolog source file "newbuiltin.P" (notice correspondence
	with the name of the predicate being defined) containing the
	definition

		newbuiltin(A,B,C,D) :- '_$builtin'(N1).

*	Compile this Prolog predicate, using the simulator and the compile
	predicate. This can be done by executing:

		% procomp newbuiltin

	in the directory lib/src. This will compile the file "newbuiltin.P" 
	and install the byte-code in the file "newbuiltin" in the library 
	directory.