The University Information Services allocates to each member of staff and student a CRSid (Common Registration Service identifier) which is used for login on a number of university systems. In addition, 3 accounts are setup, each with the CRSid as login name, viz:

Hermes, an email service.
Managed Cluster Service (MCS), consisting of clusters of PCs and Macintoshes at many locations in University Departments and Colleges, including Selwyn. These systems can be used for printing, for access to more specialist software, and for backup of important files; they are also valuable for those who do not have their own PC, or whose PC has become unuseable for some reason.
Raven, a web authentication server; used, among other things, to access the Student Information System (CamSIS), including registration for examinations.

You will receive details of your User ID, and passwords, as well as instructions on how to use them on arrival.

Some further details for new students are available at: http://www.cam.ac.uk/cs/new-students/