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If I have a USB printer, how does Linux or Windows manage the device when plugged into a different USB port? For example, I take a printer plugged into a front USB port on computer and move it to back port; Windows still recognizes that this is a printer already in use by system.

Is this just a special printer setting? A reason I ask is that I help a friend out with managing a control system (with USB digital I/O). We had to change computers out and I just plugged the USB ports into random open ports and the program still knew how to find the hardware (remember, entirely different computers)

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A USB device sends some data to the host machine called the device descriptor, which contains identifiers for:

  • The vendor of the product
  • The product itself
  • A serial number for the unit (this doesn't necessarily match the serial number marked on the device's casing)

The serial number is a way for the operating system to know whether it has seen a device before.

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3  
And some devices lack of a serial number explains why they are seen as a new device when plugged into a different port. – Richard Oct 5 '10 at 6:48

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