What is the primary function of defragmentation software?

The primary function of defragmentation software is to reorganize data on the hard drive. Over time, as files are created, modified, and deleted, they can become fragmented, meaning that pieces of a single file are scattered across different locations on the disk. This fragmentation can slow down access times since the read/write head of the hard drive has to move to multiple locations to access a single file.

Defragmentation software works by consolidating these fragmented files and reorganizing data to ensure that each file is stored in contiguous spaces on the disk. This optimization not only speeds up data access and improves the efficiency of the hard drive but also enhances the overall performance of the system.

The other options do not capture the main objective of defragmentation. Copying files to an external storage device pertains to backup processes, reducing the file size relates to compression, and encrypting sensitive information focuses on security measures, none of which are functions served by defragmentation software.