Input/Output devices are the devices that are responsible for the input/output operations in a computer system.
Basically there are following two types of input/output devices:
A block device stores information in block with fixed-size and own-address.
It is possible to read/write each and every block independently in case of block device.
In case of disk, it is always possible to seek another cylinder and then wait for required block to rotate under head without mattering where the arm currently is. Therefore, disk is a block addressable device.
A character device accepts/delivers a stream of characters without regarding to any block structure.
Character device isn't addressable.
Character device doesn't have any seek operation.
There are too many character devices present in a computer system such as printer, mice, rats, network interfaces etc. These four are the common character devices.
Here are the list of some most popular and common input/output devices: