Thursday, December 03, 2009 10:40 PM,

A student writes:



	 Dr. Patt,
	 
	 Since we are required to make two write two separate programs, is the 
	 .EXTERNAL psuedo-op a necessity?
 
	> <<name withheld to protect the student who remembers the .EXTERNAL>>



Short answer: No.

The .EXTERNAL is necessary when we have a symbol that is used in two separate 
modules where one module is loading from it or storing to it and the other 
module contains the location of the memory location.

Nothing like that exists here.  One module is the user program.  The other 
module is an interrupt service routine for servicing a request for more urgent 
attention.

Good luck with the rest of the course.

Yale Patt