IPod games are in the form of .ipg files, which are actually .zip archives in disguise. When unzipped, they reveal executable files along with common audio and image files, leading to the possibility of third party games. Apple has not publicly released a software development kit (SDK) for iPod-specific development. Apps produced with the iPhone SDK are compatible only with the iOS on the iPod Touch and iPhone, which cannot run clickwheel-based games. All iPods except for the iPod Touch can function in "disk mode" as mass storage devices to store data files but this may not be the default behavior.
IPod Touch to the iPod Touch as "training wheels for the iPhone". All iPods lack Touch ID, 3D Touch, NFC, GPS, an earpiece speaker and a noise-cancelling microphone. Depending on the generation, the iPod Touch may have a smaller or inferior display and camera(s). Newer models (5th and 6th generation) lack the ambient light sensor that makes automatic brightness available. Older models lack a built in speaker, a microphone, a camera, and a flash. No iPod Touch has a modem through which it can place phone calls or send SMS and MMS. However, 5th and 6th generation models can either piggy-back on