PRIMITIVE
	getc: get a character from standard input
USAGE
	PROCEDURE getc (VAR c: character): character;
FUNCTION
	getc reads at most one character from the standard input STDIN. If there are
	no more characters available, getc returns ENDFILE; if the input is at
	end-of-line, it returns NEWLINE and advances to the beginning of the next
	line; otherwise it returns the next input character.
RETURNS
	getc returns the value of type character corresponding to the character read
	from the standard input, or one of the special values NEWLINE or ENDFILE as
	specified above. The return value is also written in the argument c.


PRIMITIVE
	putc: put a character on standard output
USAGE
	PROCEDURE putc (c: character);
FUNCTION
	putc writes the character c to the standard output STDOUT; if the value of
	the argument c is NEWLINE, an appropriate end-of-line condition is generated.
RETURNS
	Nothing.


PRIMITIVE
	getarg: get a command line argument
USAGE
	PROCEDURE getarg (n: INTEGER; VAR str: string; maxsize: INTEGER): BOOLEAN;
FUNCTION
	getarg writes up to maxsize characters (including an ENDSTR) of the 'n'th
	command line argument into the string str. The first argument on the command
	line is argument number one. No error is reported if the argument string is 	truncated.
RETURNS
	getarg returns true if the argument is present, otherwise false.


PRIMITIVE
	nargs: get number of command line arguments
USAGE
	PROCEDURE nargs: INTEGER;
FUNCTION
	nargs determines the number of arguments used on the command line that invoked
	the program, suitable for copying by getarg.
RETURNS
	nargs returns the number of arguments found on the command line, i.e., a
	number greater than or equal to zero.


PRIMITIVE
	message: print a message and continue
USAGE
	PROCEDURE message('your message here');
FUNCTION
	message writes the literal string specified to a highly visible place, such as
	the user's terminal, then continues execution.
RETURNS
	Nothing.


PRIMITIVE
	error: print a message and exit
USAGE
	PROCEDURE error ('your message here');
FUNCTION
	error writes the literal string specified to a highly visible place, such as
	the user's terminal, then performs an abnormal exit.
RETURNS
	Nothing. Moreover, error never returns control to its caller.


PRIMITIVE
	xor: exclusive-or of a and b
USAGE
	PROCEDURE xor(a, b: character): character;
FUNCTION
	Bitwise exclusive-or of characters, also known as the symmetric sum, half
	addition, or not equivalence.
RETURNS
	The resulting character.