These quizzes may be used either as practice/self-test exercises or as assignments for student assessment.
Any (all-alphabetical) username and integer ID will allow you to log in to a set of exercises.
No information is stored on the server; a student ID number is only requested so that each student gets an individualised set of question inputs and so that, upon logging back in later with the same ID number, the student receives the same input values as before.
If you are using one of these sets of exercises for an assignment to be submitted for credit, you must use your official student ID number so that:
All students have individual assignments (i.e. 'unique' input values).
Your instructor can check your work, in the case that you are having difficulties.