PSC's PowerWedge 20 dual model is such a device. Many models allow you to attach magnetic card scanners to bar code readers. This way, you could process credit or ATM cards with the same system that reads bar codes on packages. Once you have selected an input device, you must select a decoder and the type of interface to the computer. Most batch systems use a periodic download over serial ports, and you don't have much choice in the interface method.
Interactive systems have a choice of several interfaces.
Interface types vary in ease of use. One interface may allow the user to affect the data, while another may not. This does not mean that one interface type is inherently better than another. It does mean that where user error can affect data, more follow-up will be required. The location of the readers can have a profound impact on the design of the system.