What are the structures used in file-system implementation?

Several on-disk and in-memory structures are used to implement a file system
a. On-disk structure include
1 Boot control block
2 Partition block
3 Directory structure used to organize the files
4 File control block (FCB)
b. In-memory structure include
1 In-memory partition table
2 In-memory directory structure
3 System-wide open file table
4 Per-process open table