A-LevelComputer ScienceData types and structures9618/31 · Oct/Nov 2024 · Q55 Marks

Explain what is meant by a hashing algorithm in the context of file access.

(a)Explain what is meant by a hashing algorithm in the context of file access.[3]
(b)The use of a hashing algorithm can result in the same storage location being identified for more than one record. Outline two methods of overcoming this issue. 1 2[2]

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2024). The mark or mark type is shown in brackets.

5(a) One mark per mark point (Max 3)
5(a) MP1 A hashing algorithm is used in direct access methods on random and sequential files
5(a) MP2 It is a mathematical formula
5(a) MP3 used to perform a calculation applied to the key field of the record being searched / stored
5(a) MP4 The result of the calculation gives the address where the record should be found / stored.
5(b) One mark per mark point (Max 2)
5(b) MP1 The record is stored in the next free memory space after the one identified by the hashing algorithm // Use linear progression
5(b) MP2 An overflow area is set up and the record is stored in the next free memory space in the overflow area.

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Topic: Data types and structures, A-Level Computer Science (syllabus 9618). Structured question, 5 marks.
Source: A-Level Computer Science, Oct/Nov 2024 Paper 3 Variant 1, question 5.

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