They used to type in short (3 or 4 digits) codes for the products at Aldi in Germany maybe 10 years ago. I assume they did this because the scanner technology was not as fast. The cashiers memorized the codes and were crazy fast.
Aldi Nord cashiers learned three digit codes (around 800 ones). Scanners were only introduced in 2003 because they started to sell loose produce which is weighted at the checkout. Additionally, that allowed them to get away with less training.
The checkout speed dramatically decreased since then. Before they had to pick up each and every item they often entered the numbers faster than you could load the items onto the checkout line.
6000 items per hour was the target before. Now it's around half which would have gotten you fired back in the days.
They also have full rights to the source code and in-house developers to do small changes.
The hardware is supplied by a different company that also has software on offer. But apparently that is not good enough.
Seems logical that once people have selected what they want to buy you get them out the shop as fast as possible.
But I think Aldi had a smaller varierty of products back in those days too.
Additionally, they used the same code for things like different types of yoghurt of the same size (they still have the same barcode, makes scanning faster).
Of course we have bigger stores in Germany, too. But they are not quite as profitable.
Yes, the Aldi chains were using their own system. It's not too much of a leap: they only have a few different hundred items total, and they already control the packaging and what's printed on it.
In any case, I am really glad Aldi (and Lidl) are making great inroads in the UK and Australia. Mostly because I think the incumbents in these places can use some shaking up from their cosy oligopolies. (Tesco in the UK and Coles in Australia feel `evil' in exactly the sense that we decried Microsoft to be.)