By Keyboard / Display unit I'm assuming your using a PC, thin client or dumb terminal. If you are using a PC then the easiest way to do this is to get a bar-code scanner with a USB interface, no programming should be required with possibly the exception being of adding a "Enter" (CR LR) after each scan.
If you have a dumb terminal then you may need to look at trying to use an RS232 connection (if one exists) or a keyboard wedge solution where the scanner is plugged into the keyboard port along with the keyboard.
In any event pin outs would vary depending upon the scanner you want to use and the device you are connecting the scanner to.
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