2.1 The civil service of the Central Government  is organised into four groups, viz. Group `A' (which includes all- India Service) Group `B', Group `C' and Group `D'. Such classification broadly corresponds to the rank, status and the degree of the level of responsibility attached to the posts. Group `A' posts carry higher administrative and executive responsibilities and include senior management positions in the ministries/departments and field organisations. The middle and junior levels of Group `A' alongwith Group `B' constitute middle management. Group `C' posts perform supervisory as well as operative tasks and render clerical assistances in ministries and field organisations. Group `D' posts are meant for carrying out routine duties.

2.2 The Central Services (Classification, control and Appeal) Rules, 1965 provide a concrete and specific criterion for classification of posts in terms of pay. (6). Thus, posts carrying pay or scale of pay with a maximum of not less than 13500/- are categorised under Group `A'. Posts carrying a pay or scale of pay with a maximum of not less than Rs.9000/- but less than 13500/- are known as Group `B' posts. Civil posts with a maximum pay (or a scale of pay) over Rs.4000/- but less than  Rs 9000./- are in Group `C'. The rest of the posts are in Group `D'.