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System Software: Question 1

Syllabus 5.1

Multiple choice AS 1 mark

A user's hard disk drive has been used for several years to save, edit and delete many different files. As a result, the data belonging to some files is no longer stored in one continuous section of the disk. Instead, each of these files has been split into several smaller pieces, scattered across different, non-continuous areas of the disk.

Which utility program is designed to fix this problem, by physically moving data around the disk so that each file's data is stored together again, in one continuous (contiguous) block?

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Worked solution

Why B is correct

Every time a file is saved, edited or deleted, the operating system has to find free space on the disk to store (or re-store) its data. Over time, as files of different sizes are repeatedly created, changed and removed, the free space left on the disk becomes broken up into lots of small, scattered gaps rather than one large continuous space. When a file is then too big to fit into a single one of these gaps, its data has to be split up and stored across several non-continuous areas of the disk instead. This is called fragmentation.

A disk defragmentation utility (defragmenter) is designed specifically to fix this. It reads through the disk, identifies files whose data is scattered across multiple non-continuous locations, and physically moves that data around so that each file’s data ends up stored together in one contiguous block. Because a mechanical hard disk drive has to physically move a read/write head to each location it accesses, keeping a file’s data together in one place means the head has to move around less to read the whole file, which speeds up file access.

Why the other options are wrong

  • A: A disk formatting utility prepares a storage medium for use in the first place, by writing a new, empty file system onto it, typically erasing any data already stored there. It does not reorganise the position of files already saved on a disk that is already in use.
  • C: A file compression utility re-encodes a file’s data more efficiently so the file takes up less storage space (useful for saving space or for sending a file more quickly). It does not change where a file’s data is physically stored on the disk, so it does not fix fragmentation.
  • D: An antivirus utility scans files and programs for malware, and removes or quarantines anything it identifies as a threat. This protects the computer from malicious software, but it has no effect on how a file’s data is physically arranged on the disk.

Final answer

B, a disk defragmentation utility fixes this problem, by moving a fragmented file’s scattered data together into one contiguous block on the disk, which speeds up access to that file.