IPhone (1st generation) $499, the original launch price of the 4 GB model. Apple released an SDK on March 6, 2008, allowing developers to create the apps that would be available starting in iPhone OS version 2.0, a free upgrade for iPhone users. On June 9, Apple announced the iPhone 3G, which began shipping July 11. The original iPhone was discontinued 4 days later; total sales volume came to 6,124,000 units. During release, the iPhone was marketed as running "OS X". The name of the operating system was revealed as iPhone OS with the release of the iPhone SDK. The original iPhone supported
IPhone 4S announced, it was considered by some media to be a disappointment, due to the expected release of an iPhone 5. There were no external differences between the iPhone 4 CDMA model and the , with the exception of a SIM card slot on the . All changes were internal (slight external differences between the iPhone 4 GSM model and the exist, as said differences existed between the CDMA and GSM models of the iPhone 4). On September 10, 2013, the iPhone 4S name was re-stylised as iPhone 4s, using a lower case 's' to reflect the names of the newly