In 2008, I took an internship at PT Bening Guru Semesta. My job there was to implement Openbravo ERP (Enterprise Resource Planning) and Openbravo POS (Point of Sales) to two of their clients: Tasya Baby Store & Madani Mart. Tasya Baby Store is retail chain in Indonesia which sells baby product while Madani Mart is a minimarket chain in Indonesia which sells any kinds of groceries.
I was assigned to create several module to the Openbravo ERP which are based on JSP. Another thing that was assigned to me is Openbravo POS. I have to integrate the POS system with an old printer. This need some low level programming with the printer API.
That part with the old printer is the one which is very challenging, since I couldn't find any documentation whatsoever about this particular hardware and how to integrate it with the POS system. The old dot-matrix unbranded printer seems to be manufactured in China. I had to delve into some random online forum in China to check on any slightest clue of how to operate this printer programmatically. I finally ended up just did a trial error here and there with the printer connection until I could find out how to program this printer.