Principal of I/o hardware

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Principal of I/o hardware

I/O Devices

I/O devices can be roughly divided into two categories: block devices and character devices.
  • Block Devices
    It stores information in fixed-size blocks, each one with its own address. Common block sizes range from 512 to 65,536 bytes.
    Examples are hard disks, Blu-ray discs, and USB sticks.
  • Character Device
    It delivers or accepts a stream of characters, without regard to any block structure. Not addressable and does not have any seek operation.
    Examples are printers, network interfaces, mice, and most other devices that are not disk-like can be seen as character devices.
  • Doesn't Really Fit
    Some devices don't fit into this division: For instance, clocks aren't block addressable, nor do they accept character streams. All they do is cause interrupts... at timed intervals.
    Memory-mapped screens do not fit this division either


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