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Graphics
The Graphics subsystem contains the APIs for drawing to particular types of devices, such as the screen and printers, embedding picture objects, and font and bitmap handling.

The subsystem also contains the Window Server Client-Side API, which provides functionality to draw to windows and recieve window events, and the animation APIs which allow animations to be run in a high-priority system thread.

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Application Framework
The Application Framework subsystem includes, as the name implies, the frameworks that define the application structure and their basic user interface handling. Applications here has a narrower sense than just program: it implies a program with a user interface, rather than say, a server program that runs in the background doing a system task. It can also imply a whole other group of requirements such as how the documents (data) that the application handles is presented to the user.

The scope of these APIs is actually a little larger than just that, as it also includes reusable frameworks for handling such things as text layout, user interface controls, and front end processors (non-keyboard input mechanisms, such as hand-writing recognition).

A licensee product adds its own specialist components that provide user interface elements suitable for its particular screen and input mechanisms. However, the base classes for these and many of the key application concepts are defined by this subsystem.

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Engines and utilities
The Application Engines APIs provide access to the application data of the core applications. This makes it straightforward for new applications to be integrated with the core applications: for example, for a new communications application to store manipulate and read Contacts and Agenda data.

Alongside Application Engines, as specialist manipulators of data, is the Multimedia subsystem, which provides audio and image manipulation, and Application Services, which provides a range of utility services to applications, from logging and system information, to vCard and vCalendar handling.

Finally, the Application Protocols subsystem contains components for using the connectivity standard, SyncML, and the Web HTTP protocol. The plug-in framework introduced at v7.0, ECom, is also here.

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Communications
As you would expect from a mobile phone operating system, there is a rich group of communications related APIs. They are generally smaller, and their use more specialist, than some of the APIs we have previously discussed.

The Comms Infrastructure APIs provides frameworks and system services for communications and networking. It's required background for those wishing to use particular communications technologies such as Infrared, Bluetooth, and Serial Comms. Networking also builds on the Comms Infrastructure, to provide a TCP/IP stack, and dial-up connections.

Telephony provides application access to the phone's telephony functionality, and a framework for writing drivers for particular telephony hardware. Narrow Band Protocols provides handling of SMS messaging.

At a higher-level, Messaging provides a framework for multi-protocol messaging and support for particular messaging protocols. WAP Stack provide access to a WAP protocol stack and WAP Browser adds support for WAP Push.

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Copyright ?2005  Symbian Ltd.       unknown-build-id
 
 
Overview

　　Symbian是一个很大的系统，包含了数百个类和数千个成员函数。象大部分复杂的系统一样，接触Symbain可以把它分成几个大的领域去了解，然后更加关注在你的任务中最重要的部分。比较好的分割方式叫做子系统subsystems。例如，应用程序引擎子系统包括了标准应用程序（例如联系人）所需的处理数据的所有API。

　　第三方开发者可以把任何领域和相关的功能组和看做一个子系统。他们不是类似DLL的二进制文件，也不是头文件那样的源文件。但是出于下面的原因，他们仍旧值得去被学习。
　　

　　
子系统是可以配置的，可以以很多种方式存在，子系统的一部分是必要的时候，其它部分可能是可选的。
　　
系统文档，利用子系统来组织文档的结构。

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Base

　　
　　不管是写哪一类程序，开发者都不能忽略Base子系统的A

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