Sinopsis
It’s with you all the time, ready to send and receive phone calls or messages, play alarms to wake you, connect to the phone network or other devices, organize your personal information or play games. Whatever you want to do, you want access to your phone to be instant. It should be ready without the long boot-up you expect from a PC. It should react to user input from the moment you pick it up. And it should be reliable. As a mobile phone owner, how many of your contacts’ phone numbers do you know? Your phone keeps your personal data for you and it’s essential that it doesn’t lose it.
Let’s examine the consequences of these features on the design of a mobile operating system, such as Symbian OS. The phone may be small and light, but, as users, we still demand it to have a reasonable battery life. This places huge importance on efficient power management. The operating system cannot drain the battery and must allow the processorto power parts of the system down where possible, although it cannot ever power off completely because it must handle incoming calls and messages, and signal alarms.
The user expects the phone to be responsive, not sluggish to respond to each key press; the operating system and hardware must carefully balance demands for good performance speed with the consumption requirements of power-hungry processors. Costs are also important: they limit the processor and amount of memory in a mobile device. The operating system must be efficient, to make best use of the limited
processor and memory resources available, whilst using the least power.
processor and memory resources available, whilst using the least power.
Besides being efficient, the operating system must be robust when the limited resources are exhausted. It must be engineered to cope with low memory conditions, loss of power or when a communications link is unavailable. Memory management is key. The operating system must track precious system resources accurately and free them when they are not required. It’s not acceptable for memory to slowly leak away, resulting in disintegration in performance and usability until the user is forced to reboot. The operating system should make it easy for software engineers to write code that runs without memory leaks and can handle out-of-memory conditions when they occur.
The mobile phone market is a mass market, with many millions of units shipped. It’s difficult, if not impossible, to recall them or require the user to upgrade through service packs. So when a phone is shipped, it’s shipped. It must not have any serious defects. Not only must the platform on which a phone is based be well-engineered, it must also provide the means for developers to build, debug and test robust code.
Content
- Class Name Conventions on Symbian OS
- Leaves: Symbian OS Exceptions
- The Cleanup Stack
- Two-Phase Construction
- Descriptors: Symbian OS Strings
- Good Descriptor Style
- Dynamic Arrays and Buffers
- Event-Driven Multitasking Using Active Objects
- Active Objects under the Hood
- Symbian OS Threads and Processes
- The Client–Server Framework in Theory
- The Client–Server Framework in Practice
- Binary Types
- ECOM
- Panics
- Bug Detection Using Assertions
- Debug Macros and Test Classes
- Compatibility
- Thin Templates
- Expose a Comprehensive and Comprehensible API
- Good Code Style
