1. Files
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2. Serial Files
Records are added (appended) to the end of the file as they occur.
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3. Sequential File The records are stored in sorted order of a key field.
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4. Random Access File Each record has a key field.
A calculation is performed on the key field (hashing algorithm) which results in an address (hash address).
The record is stored at the hash address.
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5. Example : A file of members of a chess club.
Each member has a 4-digit membership number. This is the key field.
Hashing algorithm : Subtract 1000 from the membership number.
Member John Smith has Membership Number 1004.
His record would be stored at record 4 in the file.
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6. Serial (sequential) Access
Each record in a file is input until the required record is found.
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7. Random (direct) Access
The hashing algorithm is performed on the keyfield of the required record, giving…
…a hash address where the record can be found.
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8. Hashing algorithm : Subtract 1000 from the membership number.
In the Chess Club example, where would the record of Sally Jones (membership number 1006) be found?
Hashing algorithm : Subtract 1000 from the membership number.
Record 6
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