iPhone OS, which bases on Unix kernel and Darwin model but is closed sourced,evolves from Mac OS X and is the default OS of iPhone, iPod Touch and iPad. Objective C based software can run in iPhone OS, and just like Android, you can develop your own iPhone applications and upload them onto Apple's 'App Store' for sale .
    　　By comparing the latest Android and iPhone OS, Android 2.2 Froyo and iOS 4, we can take a glimpse at the main feature of open and closed smart phone OSs. While the 2 OSs are designed in rather different mentality and functionality, it's a little early to tell which one is better
    　　
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    　　2. Smart Phone OS
    2.1. Android
    　　The system architecture of Android consists of 5 layers, which are Linux Kernel, Android Runtime, Libraries, Application Framework and Applications, from bottom to top.
    　　Android provides core services like security, memory management, process management, network stack and drivers, basing on Linux 2.6. Being the abstract layer between software and hardware, the layer of Linux Kernel hides the implementing details of hardware and provides integrated services for upper layer.
    　　Dalvik virtual machine and Java core libraries are included in the layer of Android Runtime, providing most functions in Java core libraries.
    　　The layer of Libraries contains a class of C/C++ libraries for Android components. Those libraries are integrated by the layer of Application Framework and then provided to developers.
    　　The layer of Application Framework provides all kinds of modules for program initialization to simplify the use of components, allowing developers do whatever they want and provide services for other softwares, under the limitation of security, of course.
    　　Mainstream applications are located in the layer of Application, including e-mail, SMS, calendar, Google map, Web browser and contacts. Users interact directly with this layer.
    　　The latest version of Android, Android 2.2 Froyo, puts on some new features. They are: 1. Support Flash 10.1, enables user to watch flash on the phone. 2. V8 JavaScript engine in web browser leads to faster Internet data transportation. 3. Big advance in network sharing. You can use the phone as a 3G NIC,or convert 3G signal to Wi-Fi. 4. Automatically software update. 5. Softwares can be setup in SD card to extend file storages.
    2.2. iPhone
    　　iPhone OS is consist of 4 abstract layers: Core OS, Core Service, Media and Cocoa Touch respectively.
    　　Layers of Core OS and Core Service are designed in C language to handle core system services, enabling developers to perform file access, sockets calling and data handling. CFNetwork and SQLite are also parts of these 2 layers.
    　　The layer of Media, according to its name, this layer is used to control video and audio, as well handle 2D and 3D images. The Open GL-ES Quratz part of the layer is coded with C language, while the part of Core-Audio and Core-Animation is Objective C based.
    　　The layer of Cocoa Touch builds a basic framework for all kinds of programs in iPhone. Most programs run in Cocoa Touch layer, and it's surely Objective C based.
    　　The latest iPhone OS is iOS 4. It includes the following new features: 1.Software classification. This
    　　feature enables user to place sorted softwares into different documents, making it clearer to manage. 2. Email integration. One account is for all e-mails from different providers. 3. iBook, originally from iPad, is built in iOS. 4. A brand new Apple Game Center makes iPhone a tremendous entertainment platform.
    2.3. Android vs. iPhone
    　　Being the top 2 smart phone OSs, we're sure that both Android and iPhone have their own advantages and disadvantages. Now let's take a look at each of them, and see what unique feature they have.
    　　Android 2.2 Froyo fully support multitask, which means you can listen to music while writing blog. And iOS 4, officially announced to be 'multitasked', is in fact a play of concept. Only a few of softwares which are authorized by Apple can run 'simultaneously', whose principle is much easier that multitask:when an application is switched out, its current state is saved and then the system just closes it. And when it's switched in, we're back to the previous snapshot.
    　　During the publication of Android 2.2 Froyo, Google announced it has 'the most fluent web browser',because the use of V8 JavaScript engine. V8 is a brand new engine, designed for running big si

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