Final answer:
At the operating system layer, symbolic file names are translated into system-level identifiers by the file system for direct or indirect file referencing.
Step-by-step explanation:
The filesystem has multiple layers of abstraction: The applications, logical file system, File-organization module, basic file system, IO control, and devices. The third layer is the physical file system. This layer is concerned with the physical operation of the storage device (e.g. disk). It processes physical blocks being read or written. In a computer, a file system -- sometimes written filesystem -- is the way in which files are named and where they are placed logically for storage and retrieval. Without a file system, stored information wouldn't be isolated into individual files and would be difficult to identify and retrieve.
At the operating system layer, symbolic file names are converted to identifiers that either reference the file directly or indirectly through a file descriptor or index table. This process involves the operating system's file system, which is responsible for managing files and directories and their organization on the disc. When a user or program specifies a file by its symbolic (or human-readable) name, the operating system's file system will translate this into a system-level identifier which may be a numerical file descriptor or an entry in an index table, such as an anode in UNIX-like operating systems.