The unlocked iPhone 4S is now officially available for purchase through Apple through their website and in Apple Stores. An unlocked iPhone is sold at a high price due to the lack of a contract subsidy, but the major advantage is that the phone can be used on any compatible GSM network through the purchase of a microsim card. In the USA, this means an unlocked iPhone would work with T-Mobile, AT&T, and some pay-go plans. Additionally, anyone in possession of an unlocked phone can use the device in another country simply by picking up a local sim card, avoiding costly roaming fees.
Resetting your mobile phone to factory condition can take care of technical problems like cramped storage or a lagging touch screen. It removes all your personal settings, including contacts, and you'll have to start from scratch or restore a backup of your data to repopulate the device. You can perform a factory reset on an unlocked phone, but it could be relocked during the process.
An unlocked phone can be used on any carrier with a service compatible with that phone. A CDMA phone can't be used on a SIM carrier even if it's unlocked; the two services are incompatible. Many phones are subsidized -- purchased for a fraction of their price with the promise of staying with the carrier for a number of years. Carriers don't unlock the phones while they're under contract.
If you've completed your phone contract with a carrier, the carrier may unlock your phone or set up a way for you to do it. AT&T, for example, allows customers with iPhones that aren't being subsidized to perform a simultaneous reset and unlock via iTunes. Verizon offers an iPhone that comes unlocked out of the box and can be reset as unlocked. Both phones must be purchased at full price to be unlocked and used with another carrier. Phones that are jailbroken and aren't unlocked out of the box or by a carrier will no longer be unlocked when they're reset to factory conditions.
Performing a factory reset on a phone returns it to its out-of-box state. All your apps and data are wiped clean and you have to go through the setup process again. If a third party reset the phone, the codes that changed the phone from locked to unlocked are removed. If you purchased the phone as unlocked before you went through setup, then the unlock should remain even if you reset the phone. If you had to enter an unlock code to unlock your phone, you should be able to use the same one after resetting your phone to unlock it again.
The only way to figure out for sure whether you can reset your unlocked phone is to contact the business or individual that unlocked it and ask whether a factory reset will wipe the unlock. If it will, ask whether it can be reset at no charge or if the person or business can perform the reset without losing the unlocked aspect of the phone. If you go ahead with the reset without discussing it with the unlocking entity, you may lose your unlock and have to pay for it again.
So now, if you walk into an Apple store and buy an unlocked iPhone, you're no longer restricted to AT&T, Verizon or Sprint. You can plug in other SIM cards. But you might experience some sticker shock. Let's compare: The Apple price on the locked 16GB phone, which only offers you a choice of AT&T, Sprint or Verizon, is $199. The unlocked version, which allows you to use the carrier of your choice, costs $649. There are comparable price differences on iPhones with more memory, too, up to 64GB.
Yesterday was a relatively big day for Android, at least compared to our regularly scheduled programming - Google sent us a gift in the form of the 4.4.3 update, available immediately via factory images and in AOSP. The problem with factory images, however, is that they require an unlocked bootloader to flash, so many of you opt in to wait for the respective OTAs. 2b1af7f3a8