This paper is written for someone who has GAP installed but no knowledge of GAP or GUAVA. For installation instructions, see the GAP web site [GAP]. Some basic knowledge of the mathematical background of error-correcting codes is assumed.
GAP 3 and above has the GUAVA package which allows one to do some coding theory explorations. We shall use GUAVA version 1.7, which requires GAP version 4.3. Everything should work in version 1.6 as well.