A-LevelComputer ScienceData types and structures9618/32 · May/June 2023 · Q25 Marks

Describe how records are organised and accessed in a sequential file.

(a)Describe how records are organised and accessed in a sequential file.[3]
(b)A hashing algorithm is used to calculate storage locations for records in a random access file. The algorithm calculates hash values using the function modulus 5. The function modulus gives the remainder after integer division. For example, 3003 modulus 5 = 3, so the record key 3003 gives a hash value of 3. Complete the table to show the remaining hash values. Record key 3003 1029 7630 Hash value 3[2]

Mark scheme

Marking points from the official mark scheme (May/June 2023). The mark or mark type is shown in brackets.

[3] One mark per mark point (Max 3) MP1 records are stored in a particular order MP2 the order is determined based on the value in a key field MP3 records are accessed one after the other MP4 records can be found by searching from the beginning of the file, record by record, MP5 until the required record is found or key field value is exceeded.
[2] One mark for each correct hash value (Max 2) Record key Hash value 3003 3 1029 4 7630 0

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Topic: Data types and structures, A-Level Computer Science (syllabus 9618). Structured question, 5 marks.
Source: A-Level Computer Science, May/June 2023 Paper 3 Variant 2, question 2.

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