A modest beginning was made during 1961 census with the adoption of “Unit record” machines. Prior to 1961 censuses, the data collection, data entry and processing were done manually. In 1961 census, the Hand Punching machines (inserting one card at a time) using 80 column (Hollirith) punch cards were used for converting data into machine readable form. The processing was done on the sample (data) selected from the entire data. Around 70 ORGI officers were involved in the data entry, programming & machine operations. The data schedules were coded at various regional tabulation centres throughout India before sending the schedules for data entry. Reproducer was used to duplicate the entire set of punched cards. Data Processing was done by using Verifiers, sorter machines. “Serial Rolling Total Tabulator cum printer (SRTT)” was used for tabulation and printing of census tables.  Data backup system was not available at that time.

 In 1971 census, the Key-punching (electrical cum mechanical) machines were used for data entry.  The machine used a stake of 80 column (Hollirith) punch cards instead of inserting cards one by one. The processing was done on the sample (data) selected from the entire data. Around 90 ORGI officers were involved in the data entry, programming & machine operations. The data schedules were coded at various regional tabulation centres throughout India before sending the schedules for data entry. An IBM 1401 computer along with IBM card reader and printer was used at the Headquarter at New Delhi for processing. The large size spools of magnetic tape were used for data processing and for keeping backup storage.

 In 1981 Census, first time in Indian census, the data entry activities were decentralised and 15 data centres were setup in major states including at one at headquarters, ORGI. Each centre was allotted more than one state (adjoining states) to convert paper-based information into machine-readable form using “key to disk” machines provided by GCS, ECIL & ICT. The data processing was done using HP1000, CD-Cyber 730 & NEC-1000 computer   systems at NIC, New Delhi and Regional Computer Centre (RCC), Chandigarh. The in-house data processing facilities were not available in ORGI.  The data schedules were coded at various regional tabulation centres throughout India before sending the schedules for data entry  to allotted one of the 15 data centres. Around 1200 ORGI officers including officers at 15 data centres, were engaged for the entire census data processing activities. All the required software (for data validation, editing, processing and tabulation) were developed by the officers of Data Processing Division, ORGI, Headquarters.

 During 1991 Census, a drastic change in the data processing activities in ORGI was taken place. ORGI had setup its own computing facility by installing Medha-930 main frame system at DP Division, Pushpa Bhawan. Dump terminals, under Unix operating system, connected to the servers at 15 data centres, were used for data entry.  Data movement between various data centers and Computer centre at Delhi was done through magnetic tapes. The data schedules were coded at various regional tabulation centres (about 163) throughout India before sending the schedules to the allotted one of the 15 data centres for data entry. Master data files creation, data editing on basic fields and lower level tabulations were processed at 4 Regional Processing Centres namely Delhi, Bhopal (Madhya Pradesh), Bhubaneshwar (Orissa) and Chennai (Tamil Nadu). Major editing considering all the fields, processing and generation of all the tables at various levels were taken up in DP Division, ORGI, HQr. All the required software (for data validation, editing, processing and tabulation) were developed by the officers of Data Processing Division, ORGI, HQr. First time, in the 1991 census, DP Division generated the camera ready copies of the tabulations in Hindi as well as in English for publication. The cent percent data was captured. The processing was done on the cent percent data of workers & SC/ST. Only 10 per cent records were processed for other tabulations. Around 1200 ORGI officers including officers at 15 data centres were engaged for the entire census data processing activities. The software were developed in-house by DP Division officers.