The Department of Computer Science maintains an account, called the "PhD pool", which provides a uniform level of basic support for working expenses for PhD education. PhD students can apply for support from the PhD pool to the following kinds of expenses:
All expenses must be approved (by main supervisor and the head of the CS PhD committee). The PhD pool also covers expenses for the annual PhD retreat. Your supervisor may be able to provide additional support (e.g. for special IT equipment or project-specific traveling).
Most - but not all - PhD students at the department are covered by the PhD pool. If in doubt, ask your supervisor or the head of the CS PhD committee.