Editing Atari interface (section)

===Atari 2600 keypads===
Atari released several keypads for the Atari 2600 that all worked the same way.
They were supported by some Atari's 8-bit computer software as numeric keypads, albeit using telephone layout (1,2,3 at top, * and # keys) instead of calculator layout (1,2,3 at bottom and decimal point). All use calculator-style buttons.

The switches are exposed as a 3×4 [[Keyboard matrix|matrix]] using the direction, trigger and pot lines. This worked on Atari machines because some pins could be configured as output in software.<ref name="atari400hwm1">[http://www.atarimania.com/documents/atari-400-800-hardware-manual.pdf Atari 400/800 Hardware Manual], Dated 1982. Retrieved from [www.atarimania.com AtariMania] on 2018-04-24</ref>

* The CX21 ''Keyboard Controller'' has the digits, and * and # symbols printed on a label. They were sold in pairs and can be slotted together.
* The ''Basic Programming'' controllers were a pair sold with a very primitive BASIC programming cartridge. The hardware is the same as the Keyboard Controllers but with different printed labels. The program uses four layers that are toggled between by pressing a button on the left controller.
* The ''Video Touch Pad'' uses a paper overlay over unlabelled rectangular buttons. Different paper overlays were supposed to be distributed with different games, but only one game is known. 
* The ''Kid's Controller'' (for games from the Children's Television Workshop) uses larger circular, numbered buttons and different larger overlays than the Video Touch Pad.

The idea of having a numeric keypad with overlays was reused later for the Atari Jaguar gamepad.