To call a routine from the call.c program (an example or two are already
in there) you put the code you want to call within the program and make
entries in the places indicated (see the examples hello and get_addr).

Then, compile the code and link it to the engine by issuing the following
command:

make appx -f Makefile.callable

This will compile the file call.c and then link the executable code into
the appx engine.

To call the required routine, eg. hello, you would include a CALL statement
within the ILF code where you want the routine to be called. In the case of
the hello routine, the line would be:

	CALL		.hello			RESIDENT? N END? N FAIL 0

Another example is included, this is called get_addr and this routine
will return the address of the first parameter passed to it as the second
parameter.  The necessary PASS and CALL statements to execute this routine
are:

	TRAP
	PASS	---	TEMP 79			FIELD		SHARE? Y
	PASS	---	AI			FIELD		SHARE? Y
	CALL		.get_addr		RESIDENT? N END? N FAIL? 0
	SET	---	AI			=	---	AI

This will show that AI, initially zero, will contain the address of TEMP 79
upon returning from get_addr.

Note: the leading period in the call to the function is required.
