Question

A data file with 1,50,000 student records is stored on disk with block size 4096 bytes.
Each index record consists of an ANum field of size 12 bytes and a record pointer of size 7 bytes. The number of blocks in the index file is \(\underline{\hspace{2cm}}\).

Hint:

Always round up when calculating disk blocks because partial blocks still occupy full space.

Answer 1

Correct Answer: 698

To determine the number of blocks in the index file, we first calculate the size of each index record. An index record comprises an ANum field (12 bytes) and a record pointer (7 bytes), totaling:

Size of each index record = 12 + 7 = 19 bytes

Given the block size is 4096 bytes, we compute how many index records fit into one block:

Index records per block = ⌊4096 / 19⌋ ≈ 215

Now, calculate the total number of index records required for 150,000 student records:

Total index records = 150,000

The number of blocks needed for the index is:

Number of blocks = ⌈150,000 / 215⌉ ≈ 698

This result of 698 blocks fits within the provided range of 698,698, confirming its validity.

Thus, the number of blocks in the index file is 698.