CID is an abbreviation for Chalmers IDentity, a combination of letters (and sometimes digits) that uniquely identifies a person. The CID is often based on the persons names, but does not need to be that.
A CID is always written in lowercase when used.
Your CID, in combination with your Chalmers password, are often used to login to computers and systems. Some systems require you to type your CID in a special way, other systems use the CID but have a special password
For more information about CID:
it-portal | Faq / Vad är ett CID?
Change CID password: