As you asking for basic rules related to Common Admission Test (CAT) , so on your demand here I am telling same for you :

Common Admission Test (CAT) is the gateway to the cream of management institutes in India, the IIMs.

Eligibility rules
Applicants must be a graduate with 50% marks or equivalent CGPA (45% in case of SC/ST/DA/PWD) or possess an equivalent qualification recognized by the ministry of HRD, Government of India.


Applicants appearing for the final year of bachelor’s degree / equivalent qualification examination and those who have completed degree requirements and are awaiting results can also apply. (Applicants if selected needs to submit a certificate latest by 30th June 2016 from the Principal/Registrar of College/Institute stating that the Applicants has completed all the requirements for obtaining the bachelor’s degree/equivalent qualification on the date of the issue of the certificate.)


Reservation:
15.00% Scheduled Caste (SC)

7.50% Scheduled Tribe (ST)

27.00% Other Backward Classes (OBC) candidates belonging to the “non-
creamy” layer

3.00% Differently Abled (DA)

For more details on the eligibility criteria and reservations,


Exam Pattern

Section No. of Questions Duration
1. Quantitative Ability
34 3 hrs
2. Verbal Ability & Reading Comprehension
34
3. Data Interpretation & Logical Reasoning
32
Total 100