iPhone 3G:The second model
The iPhone 3G is the second generation of the Apple iPhone. It was introduced on June 9, 2008, at the WWDC 2008 which was also held in San Francisco at the Moscone Center. This device is very similar to the first model. The similarity goes beyond physical appearance, which is identical. The performance of the second generation is limited by the same MB unit of eDRAM and the quality of its photographs is limited by the same 2 megapixel camera that doesn't support video recording. However, the second generation has several improvements from the first one, like Assisted GPS, 3G data or Quad-band UMTS/HSDPA.
The device uses Apple's iOS (first called iPhone OS) operating system which is based on the Machintosh Mac OS operating system which is also developed by Apple. Like in the case of the first generation, the iPhone 3G can run a huge number of applications. However, these applications, called Apps, must be checked and approved by Apple itself and obtained through their online webstore. If you install applications that don't meet the requirements on your iPhone, your device may suffer sever software malfunctions which will not be covered by the warranty. The control of the iPhone is based on the 3.5 inch MultiTouch liquid crystal display. The touch screen was developed for bare hands usage, so normal styluses and gloves do not work on the device. However, if you care for it that much, you could always buy a special developed stylus or glove which works on the iPhone too.
The iPhone 3GS: Third model
The first two generations had the needed amount of succes in order for Apple to release a third model. This happen in 2009, at the WWDC 2009 in Moscone Center (San Francisco). This model hasn't got too many improvements, just a few in the hardware range, regarding performance and speed ( it is believed that the "S" in "iPhone 3GS" stands for "Speed" ). Improvements still exist, however, like the higher resolution photo camera which is now able to perform video recording, or the support for 7.2 Mbit/s HSDPA downloading (uploading remained at 384 Kbps due to Apple not implementing the HSUPA protocol on the device).
The device runs on a Samsung chip, and a PowerVR GPU. It has an 800 Mhz Cortex-A8 CPU undercloked at 600 Mhz, and 256 MB of eDRAM. The extra amount of eDRAM is for supporting higher performance and multitasking in iOS 4. The iPhone 3GS runs the same iOS operating system and is controlled by the same MultiTouch based 3.5 inch screen as the first two generations.