These simple scanners are either physically connected to a PC or computer terminal with a cable, or they're communicating via a “cordless” (RF) connection. Either way, the scanner output is almost always directly interacting with whatever software is running on the computer screen by sending the bar code data as keystrokes, wherever the data input cursor is located. This means that an on-line bar code scanner can probably function with any off-the-shelf software, since the scanner is simply emulating a keyboard!
A tethered on-line scanner is interfaced with a compatible port on the computer: USB, keyboard, or serial RS-232 being the most common types. The length of the cable is a standard 2m (6’) or so and is typically limited to a total length of around 6m (20'). Tethered scanners are available in many form factors and styles. Most common are: wand (pen), gun-type, flashlight style, and omnidirectional (most commonly used in point-of-sale applications).
Most cordless scanning systems use Bluetooth as the open wireless communications technology, indicating a transmission range of up to 10m (Class 2) or 100m (Class 1), depending upon the transmitter (scanner) and receiver device. So, a cordless on-line scanner transmits the bar code data through an RF connection between the battery-powered scanner and a Bluetooth-embedded “base station” or a Bluetooth receiver component embedded in a computer or attached to a computer, most commonly as a USB dongle.
A memory scanner is not all that common – but is perfect in many business situations where something ultra-simplistic is perfect. Looking and acting much like a cordless scanner, a memory scanner simply scans and stores bar codes in its memory. When you've finished collecting bar codes, you just bring the scanner to a PC and transmit the contents of its memory into an active software program. Note that because memory scanners aren’t all that “smart,” they typically cannot be programmed to distinguish between suitable bar code symbols and those that aren’t, making them suitable only for “quick and dirty” situations and where business rules control the use of the scanner.