1. Character devices are read and written directly without buffering.

2. Block devices can only be written to and read from in multiples of the block size, typically 512 or 1024 bytes. Block devices are accessed via the buffer cache and may be randomly accessed, that is to say, any block can be read or written no matter where it is on the device. Block devices can be accessed via their device special file but more commonly they are accessed via the file system. Only a block device can support a mounted file system.

3. Network devices are accessed via the BSD socket interface and the networking subsytems described in the Networking chapter.

The Raw devices are character devices (major number 162).

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