Transforming I/O Requests to Hardware Operations

We now explain how the operating system translates a service request from a user program to actions performed by hardware.

• A user application can specify what data to access by mentioning the name of the file that contains the data.
• Windows apps will use a string and a colon, such as "C:/", to indicate the name of the device.
• In Linux and Mac, devices could be accessed using their absolute paths, such as "/dev/hda". The leftmost "/" forward slash stands for the root folder.
• Linux and Mac use special device files, usually located in the "/dev/" directory, to represent and access physical devices directly.
• The operating system could also use lookup tables, which will facilitate the search for connected devices.

The following flow chart shows the life cycle of an I/O request that involves reading data from a device.