Here are police ranks for Pakistani Police.
INSPECTOR in most cases is SHO ( STATION HOUSE OFFICER ... GRADE 11 )
ASI or ASSISTANT SUB INSPECTOR can also take the charge of certain check posts. carries out forward investigations, handles most of the daily responsibilities. documentation etc.
SI or SUB INSPECTOR is mostly attached to SHO and is incharge of POLICE STATION LIMITS PATROL and is often OFFICIALLY ATTACHED to the S.H.O . senior SI can also take charge of the police station in the absence of INSPECTOR ( S.H.O )
INSPECTOR or S.H.O station house officer is totally responcible for the respective police station
ASP equivalent to CAPTAIN of Pakistan Army is a direct officer in grade 17 recruited through the CSS exam conducted by FPSC.. the ones recruited through this exam are rapidly promoted throughout service as compared to promoted officers.
ASP is responsible for 2 or more police stations. and more than 2 SHOs are under his command
DSP does the same job as ASP but he is a promoted officer from the lower ranks and DSPs and promoted officers dont experience rapid promotion in service. most of them retire as DSPs. either they are recruited as constables and make their way upto DSPs if they are lucky enough. or ASIs or SIs or direct INSPECTORS... the promoted officers are recruited via provincial civil service
— with ASP ( GRADE 17 ) Direct Officer ( Recruited through CSS Exam ) and DSP ( GRADE 17 ) Promoted Officer from lower ranks such as constable, ASI, SI, Inspector. With SP ( GRADE 18 ), DIG ( GRADE 20 ), SSP ( GRADE 19 ), ADL. DIG ( GRADE 21, ASST. IG ( GRADE 19 ) and IG ( GRADE 22 ).