Section 4 in 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.
