About your program. Look at your core courses. From here,
http://future.mcmaster.ca/programs/compsci/
This tells me you're doing math and programming for the most parts to understand coding and the mathematics behind it.
Electives are option courses to your degree. They supplement your interests. You can take whatever you want. You can take a language, learn business, etc or easy courses to boost your marks. As long as they are under the approved list.
www.eng.
mcmaster.ca/documents/
electives.pdf