When the operating system marks cluster as used, but does not allocate them to any file, these clusters are known as __________.

• A. Bad clusters
• B. Empty clusters
• C. Lost clusters
• D. Unused clusters

Answer: (C)

When the file system marks a cluster as used but no file or directory references that cluster, it becomes detached from any data chain. These orphaned or detached clusters are called lost clusters. They’re not accessible through any file path, and they often result from file system corruption, improper shutdowns, or disk errors. They’re different from free or unallocated space, which is available for new data, and from bad clusters, which are defective and unusable. Disk check tools may detect lost clusters and attempt to recover any data that may still be recoverable.