Sitting in on unitsA PhD is necessarily very specialised: you become an expert on a very specific topic. Furthermore a PhD is a lot of work and it's tempting to focus on it to the exclusion of everything else. A research assistantship is similar. Becoming an expert in one area is good but at the same time you want to be a well-rounded computer scientist. You want to be able to talk to (and collaborate with, and rate proposals from) people outside your immediate area. This is a lifelong learning process, especially in a fast-moving subject like computer science.
To become better-rounded you'll have to make time to learn about things outside your area. Attending seminars and sitting in on units are good ways to do this, and your advisor should support you in this.
We're all busy but you will find it easier to make the time as a PhD student (unless you are writing up) or RA than when you have some other full-time job!
Registering for voluntary unitsAs a courtesy you may want to ask the unit lecturer if you can sit it on the unit. You can register for CS units as "voluntary unit" so that you'll be on the mailing list in case of timetable changes or other announcements. This will also allow you to submit assignments and have them marked, if you so wish. To register see Ian Holyer.
It's also possible to register units outside CS as voluntary units by talking to the department in question.
To sit an exam you would need to make a special arrangement because the faculty becomes involved at that point.
There does not seem to be any system for recording credits when a PhD or RA completes a unit but if you are keen to do so it might be possible.
How to find units
From the department teaching page you can find links to:
- All CS units (note units commencing COMS9... are not real units).
- A list of external units commonly taken by CS students.
- The University's main list of units.
Apparently the Maths department has booklets and timetables for all courses just inside the main door of their building, and these are easier to use than their web pages.