Organization of I/O Function
The computer system’s interface to the outside world is its I/O architecture. This architecture is designed to provide a systematic means of controlling interaction with the outside world and to provide the operating system with the information it needs to manage I/O activity effectively.
Every I/O device in UNIX is associated with a special file, these are managed by the file system and are read and written in the same manner as user data files. This provides a clean, uniform interface to users and processes. Read and write requests are made for the special file associated with the device to read from or write to a device. There is a file subsystem that manages files on secondary storage devices and it also serves as the process interface to devices.
For windows, the I/O manager is responsible for all I/O and provides a uniform interface that all types of drivers can call. The I/O manager works closely with four types of kernel components and these are cache manager, file system drivers, network drivers and hardware device drivers. There are two modes of I/O operation in windows, asynchronous and synchronous.