A Barcode reader or Barcode scanner is an electronic input device which is able to scan and decode barcodes.

Is a barcode reader or output?

Like other input devices, a barcode reader is bringing in (inputting) information from the outside world into a computer or other electronic device. If the barcode reader also has a screen that displays (outputs) results or prints results, it would be considered an input/output device.

Is reader input or output?

It is a input device and also an output device. Most early computers, such as the ENIAC, and the IBM NORC, provided for punched card input/output. Card readers and punches, either connected to computers or in off-line card to/from magnetic tape configurations, were ubiquitous through the mid-1970s.