IPhone is a line of smartphones designed and marketed by Apple Inc. The iPhone line of products use Apple's iOS mobile operating system software. Apple has released eleven generations of iPhone models, each accompanied by one of the eleven major releases of the iOS operating system. The original iPhone was described as "revolutionary" and a "game-changer" for the mobile phone industry. Newer iterations have also garnered praise, and the iPhone's success has been credited with helping to make Apple one of the world's most valuable publicly traded companies.