The Central Civil Services (Classification, Control & Appeal) Rules, 1965
4. CLASSIFICATION OF SERVICES:
(1) the Civil Services of the Union shall be Classified as follows:-
(i) Central Civil Services, Group 'A';
(ii) Central Civil Services, Group 'B';
(iii) Central Civil Services, Group 'C';
(iv) Central Civil Services, Group 'D';
(2) If a Service consists of more than one grade, different grades of such Service may be included in different groups.
Government of India Decisions: