Hierarchical file system

[2] This is organized as a tree structure, or hierarchy, generally portrayed with the root at the top.

The root directory is the base of the hierarchy, and is usually stored at some fixed location on disk.

Specifying a dataset name without specifying a serial number in JCL implies a catalog search.

The "root directory", a dataset named SYSCTLG, may contain file pointers or links to subdirectories called CVOLS.

IBM virtual storage operating systems replaced SYSCTLG with a VSAM Catalog.

The program "Access Method Services" (IDCAMS) maintains the VSAM Catalog.

DOS 2.0, which supported hard disk drives, introduced a hierarchical file system.

The hierarchical file system was used instead of simply expanding the flat directory for performance reasons.

"[2] OS/2 and Windows also support a hierarchical file system, using the same path syntax as DOS.