Costs

• We'll see many different methods for searching and maintaining flat files

• They all have tradeoffs

• Some support quick searches

• Some support quick modifications

• There's always a tradeoff

                             Copy the file

        Add record            S
        Delete record         S
        Modify record         S

• Here S is the size of the file

• This means that it takes about twice as long to deal with a file that is twice as big.

        Successful search     S/2
        Unsuccessful search   S

• On average, we only have to search half the file if the record is there

• But the whole file if not

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Copyright © 2003 M. J. Dominus