Add subtractor, which computes onen trit in the difference not as expected.
treed6dfd44d8204445cb35ece94b65e7825704d684d
-rw-r--r-- 32 .gitignore
-rwxr-xr-x 230912 Spring 2008 Schedule.mpp
drwxr-xr-x - asm
drwxr-xr-x - bb
drwxr-xr-x - circuits
drwxr-xr-x - digital_simulator