Some iPhone games try to emulate the kind of layout you'd see on an actual video game controller -- a directional pad on the left and a set of A/B/C buttons on the right. That's a familiar configuration, it allows for a lot of options, and the developer can let the player customize just how everything's laid out.
Source: http://www.technewsworld.com/rsstory/72008.html
SYNOPSYS SYNNEX SYMANTEC SYKES ENTERPRISES INORATED