They process credit cards, send orders to computer screens in kitchens and help run loyalty programs. In the industry, they're called point-of-sale, or POS, systems, and vary greatly in what they can do.
The register malfunction that forced Starbucks to close stores last week was surprisingly large; it affected all company-owned stores in the U.S. and Canada, or more than 60 percent of roughly 13,500 locations.
"I have never heard of anything on a national scale like this," said Blaine Hurst, chief transformation and growth officer at Panera Bread Co.
Starbucks said the outage was the result of an "internal failure during a daily system refresh," and declined to provide further details.
Regardless of the shutdown's cause, modern-day registers have become an essential tool for helping restaurants with: