Logical File System
Responsible for providing the before discussed interface to the user including:
- File access.
- Directory operations.
- Security and protection.
At the initial level device drivers communicate directly with the peripherals or their controllers or channels. A device driver is accountable for starting I/O operations on a device and processing the completion of an I/O request. For file operations the usual devices controlled are disk and tape drives. Device drivers are generally considered to be part of the operating system.
The next to initial level is referred to as the basic file system or the physical I/O level. This is the foremost interface with the environment outside of the computer system. The-basic I/O administrator is responsible for all file I/O initiation and termination. At this level control structures are sustain that deal with device I/O scheduling, and file status. The basic I/O administrator is apprehension with the selection of the device on which file I/O is to be performed on the basis of which file has been selected. It is as well concerned with scheduling disk and tape accesses to optimize performance.
Logical I/O makes possible users and applications to access records. Therefore whereas the basic file system deals with blocks of data the logical I/O module deals with file records. Logical I/O supplies a general-purpose record I/O capability and maintains basic data about files.
The level of the file system contiguous to the user is often termed the access method it provides a standard interface between applications and the file systems and devices that hold the data. Different access methods replicate different file structures and different ways of accessing and processing the data.