The first electronic computers were used for calculations in scientific applications. The
volume of data in these applications was very small and the number of computations were
very large in number. Later on, it was realized that computer could be useful for business
applications such as payroll, banking, railway and airline reservation, inventory control,
design work etc. where the volume of data is very large in comparison to scientific applications.
The program and data must be brought into main memory before processing takes place.
The computer memory being limited so the entire data may not even fit into main memory. Even
if, it fits into memory, the entire data is not processed at a time. Generally, only a small
amount of data is processed at a time, so why to keep the main memory occupied with
unnecessary data. The unused memory space can be utilized by other programs or data. The
above mentioned problems required the use of files.