- Количество слайдов: 18
The Basics of Symbian OS Communication ICT 3213 – Mobile Operating System FOEIT – INTI International University
Six elements that combine to make up Symbian OS n n n The core OS, commonly called a kernel [a bridge between application and actual data processing done at the hardware level] A collection of middleware for system services [Software that provide a link between separate applications] A set of resource managers, called application engines A framework for designing user interfaces Methods for synchronization with other machines A Java virtual machine implementation The Software: n Kernel- responsible for managing the system’s resources n Middleware- connects software components or applications; facilitates applications such as security, web browsing, messaging, etc… n Application execution environment- application programming interfaces that allow developers to create their own programs n User interface framework- graphics and layouts n Application suite- basic applications that users access regularly
System view of Symbian OS(Framework)
Architecture… [Symbian/Android Architecture] UI Framework Java J 2 ME Application Services OS Services Base Services Kernel Services & Hardware Interfaces Generic OS Services Comms Framework Telephony Services Short Link Services Networking Services Low Level Libraries Kernel Architecture Multimedia & Graphic Services File Server Connectivity Services
Kernel Services & Hardware Interface. . n n n Bootstraps[area for bootingpurpose] the physical or emulated device Provides physical and logical device drivers and other hardware abstraction Creates and manages the fundamental OS kernel abstractions n Kernel layer, contains the OS kernel itself, device drivers, and similar low-level components In term of Processes, memory management, scheduling, interrupts, communication link etc.
Base Services. . Lowest level of user-side services, extends the OS kernel into a useable (but minimal) system [drivers & library located here] n n n It includes the File Server and User Library: C++ Classes, native type Plug-In Framework which manages all plug-ins: Power Mgmt Store : Central Repository, DBMS Cryptographic services Services for a functional port
OS Services. . Generic OS Services n Connectivity Services n n n “Middleware" layer of Symbian OS, full range of servers, frameworks, and libraries[now is high level ] which extend the base system into a complete OS [where it provides framework & libraries that extends into a complete OS] Multimedia & Graphics Services Extends the "base" into a fully functional OS providing services across a full range of technologies, e. g. graphics & multimedia, Communications, Connectivity, etc. Generic: certificate mgmt Communications: Bluetooth, Infrared, USB, TCP/IP, Wi-Fi Connectivity: backup&restore, file transfer, file browsing, etc.
Semaphore = An abstraction for controlling access by multiple processes to common resource in a parallel programming environment.
Application Services. . n UI independent support for applications, n Generic - text rendering, MIME content handling, etc. Application specific – plug-ins for contacts, agenda, Word, Sheet, etc. Technology-specific - v. Card, VCal, etc. n n n including basic application frameworks/services application class (“technologyspecific”) logic support for specific applications. Also some application engines used and extended by licensees
UI Framework. . n n Topmost layer of Symbian OS, foundation for variant UI n n Frameworks and libraries for constructing a UI Includes the basic class hierarchies for UI controls Concrete widget classes used by UI components Other frameworks and utilities
Java J 2 ME MIDP. . n Java J 2 ME MIDP 2. 0 and CLDC 1. 1 n n Spans the UI Framework and Application Services layers Java implementation based on J 2 ME MIDP 2. 0 and CLDC 1. 1 Optional packages: 3 D grahics, web services, file system access, etc.
Key Characteristics n. Integrated multimode mobile telephony Symbian OS integrates the power of computing with mobile telephony, bringing advanced data services to the mass market n. Open application environment – Symbian OS enables mobile phones to be a platform for deployment of applications and services (programs and content) developed in a wide range of languages and content formats n. Open standards and interoperability – With a flexible and modular implementation, Symbian OS provides a core set of application programming interfaces (APIs) and technologies that is shared by all Symbian OS phones. Key industry standards are supported n. Multi-tasking – Symbian OS is based on a micro kernel architecture and implements full multi-tasking and threading. System services such as telephony, networking middleware and application engines all run in their own processes n. Fully Object-oriented and component based – The operating system has been designed from the ground up with mobile devices in mind, using advanced OO techniques, leading to a flexible component based architecture n. Flexible user interface design – By enabling flexible graphical user interface design on Symbian OS, Symbian is fostering innovation and is able to offer choice to manufacturers, carriers, enterprises and end-users. Using the same core operating system in different designs also eases application porting for third party developers.
Features n n n Client-Server Architecture n In Symbian OS, clients are programs that have user interfaces, and servers are programs that can only be accessed via a well defined interface from other programs Event Management n Event management has long been considered core strength of Symbian OS - reflecting the fact that Symbian OS was designed from the start to have event based time sharing in a single thread Object Oriented Design n Because Symbian OS has an object oriented design, it is easy to configure for different sorts of hardware, and being component based, it allows manufacturers to add or remove components n This will provide a stable base as the telecommunications industry moves from 2 G to 2. 5 G to 3 G to 4 G, with the further introduction of new technologies such as Sync. ML, Blue. Tooth, and Multimedia Messaging amongst many… Power Management n Symbian OS users are used to the performance of mobile phones - and so demand similar performance in terms of weight and operating times when they adopt new devices n Power management is built into the kernel of Symbian OS and is designed to make efficient use of the processors and peripherals and so minimize power usage Robust and Dependable n Devices should not lose user data, crash or require rebooting n Symbian achieves this in two ways: n Each process runs in a protected address space, thus it is not possible for one application to overwrite another’s address space. The kernel also runs in a protected address space, so that a bug in one application cannot overwrite the kernel’s stack or heap.
Features n n Robust and Dependable n Symbian achieves this in two ways: n The client-server architecture of Symbian OS allows applications to exchange data without compromising overall system integrity. This meets the requirement to work on stand alone portable devices, even though Symbian devices offer greatly enhanced functionality over standard mobile phones. Memory Management n For stand alone portable devices, memory management is important n The need to minimize weight, device size and cost means the amount of memory available on a Symbian OS device is often quite limited n Symbian OS always assumes that the memory available is limited, and minimizes consumption at every turn n Consequently, less memory is actually required by the system also having less memory helps to keep down power consumption Full Multitasking n Symbian OS runs each application as a separate process, allowing multiple applications to run concurrently An Operating System n Symbian OS is an open OS n Open to anyone to license n Open to anyone to develop application n Based on open standards n Owned by the industry
Strengths n Memory Management n The absence of demand-paged virtual memory does not mean the absence of memory management, smaller platforms are built on hardware that includes many of the management features of larger systems n Execution in-place n Platforms with no disk drives usually support execution in-place n Flash memory is mapped into the virtual address space and programs can be executed directly from flash memory, without copying them into RAM first Weakness n No Virtual Memory n The only storage available to the operating system on these platforms is memory; they do not come with a disk drive n Smaller systems, from PDAs to smartphones to higher level handheld devices, do not support a demand paged virtual memory
4) Explain how Symbian operating system addresses the memory. Ans: How Symbian OS Addresses Memory? n Symbian OS is a 32 -bit operating system, addresses can range up to 4 GB n Symbian OS divides memory into virtual pages and physical frames n Symbian OS adopts a two-level page table strategy (shown in next slide)