Direct organization eliminates the need for an index by translating each record's key field directly into a disk address. The computer does this by applying mathematical formulas called hashing algorithms. Several hashing procedures have been developed .One of the simplest involves dividing the key field by the prime number closet to, but not greater than, the number of records to be stored. The reminder of this division procedure becomes the relative address at which the record will be stored. Consider a reasonably straightforward example, Suppose that a company has 1,000 employees and therefore. 1,000 active employee numbers. Suppose also that all employee identification numbers are four digits long.
Therefore, the possible range of ID numbers is from 0000 to 9999.Assume that this company wants to store the record of Employee 87422 on disk. The hashing procedure defines a disk address as follows: The computer determines the prime number closest to 1,000 to be 997.After placing the record at an address corresponding to this number, the computer can retrieve t as needed by applying the aging procedure to its key field again. The computer can usually calculate an address I n this manner in much less time than it would take to search through one or more indexes.
Therefore, the possible range of ID numbers is from 0000 to 9999.Assume that this company wants to store the record of Employee 87422 on disk. The hashing procedure defines a disk address as follows: The computer determines the prime number closest to 1,000 to be 997.After placing the record at an address corresponding to this number, the computer can retrieve t as needed by applying the aging procedure to its key field again. The computer can usually calculate an address I n this manner in much less time than it would take to search through one or more indexes.
