Wednesday, 12 October 2011

What is Android?

Android is a software stack for mobile devices that includes an operating system, middleware and key applications. The Android SDK provides the tools and APIs necessary to begin developing applications on the Android platform using the Java programming language.

Features

  • Application framework enabling reuse and replacement of components
  • Dalvik virtual machine optimized for mobile devices
  • Integrated browser based on the open source WebKit engine
  • Optimized graphics powered by a custom 2D graphics library; 3D graphics based on the OpenGL ES 1.0 specification (hardware acceleration optional)
  • SQLite for structured data storage
  • Media support for common audio, video, and still image formats (MPEG4, H.264, MP3, AAC, AMR, JPG, PNG, GIF)
  • GSM Telephony (hardware dependent)
  • Bluetooth, EDGE, 3G, and WiFi (hardware dependent)
  • Camera, GPS, compass, and accelerometer (hardware dependent)
  • Rich development environment including a device emulator, tools for debugging, memory and performance profiling, and a plugin for the Eclipse IDE

Android Architecture

The following diagram shows the major components of the Android operating system. Each section is described in more detail below.



Android System Architecture

Applications


Android will ship with a set of core applications including an email client, SMS program, calendar, maps, browser, contacts, and others. All applications are written using the Java programming language.

Application Framework

By providing an open development platform, Android offers developers the ability to build extremely rich and innovative applications. Developers are free to take advantage of the device hardware, access location information, run background services, set alarms, add notifications to the status bar, and much, much more.
Developers have full access to the same framework APIs used by the core applications. The application architecture is designed to simplify the reuse of components; any application can publish its capabilities and any other application may then make use of those capabilities (subject to security constraints enforced by the framework). This same mechanism allows components to be replaced by the user.
Underlying all applications is a set of services and systems, including:
  • A rich and extensible set of Views that can be used to build an application, including lists, grids, text boxes, buttons, and even an embeddable web browser
  • Content Providers that enable applications to access data from other applications (such as Contacts), or to share their own data
  • A Resource Manager, providing access to non-code resources such as localized strings, graphics, and layout files
  • A Notification Manager that enables all applications to display custom alerts in the status bar
  • An Activity Manager that manages the lifecycle of applications and provides a common navigation backstack
For more details and a walkthrough of an application, see the Notepad Tutorial.

Libraries

Android includes a set of C/C++ libraries used by various components of the Android system. These capabilities are exposed to developers through the Android application framework. Some of the core libraries are listed below:
  • System C library - a BSD-derived implementation of the standard C system library (libc), tuned for embedded Linux-based devices
  • Media Libraries - based on PacketVideo's OpenCORE; the libraries support playback and recording of many popular audio and video formats, as well as static image files, including MPEG4, H.264, MP3, AAC, AMR, JPG, and PNG
  • Surface Manager - manages access to the display subsystem and seamlessly composites 2D and 3D graphic layers from multiple applications
  • LibWebCore - a modern web browser engine which powers both the Android browser and an embeddable web view
  • SGL - the underlying 2D graphics engine
  • 3D libraries - an implementation based on OpenGL ES 1.0 APIs; the libraries use either hardware 3D acceleration (where available) or the included, highly optimized 3D software rasterizer
  • FreeType - bitmap and vector font rendering
  • SQLite - a powerful and lightweight relational database engine available to all applications

Android Runtime

Android includes a set of core libraries that provides most of the functionality available in the core libraries of the Java programming language.
Every Android application runs in its own process, with its own instance of the Dalvik virtual machine. Dalvik has been written so that a device can run multiple VMs efficiently. The Dalvik VM executes files in the Dalvik Executable (.dex) format which is optimized for minimal memory footprint. The VM is register-based, and runs classes compiled by a Java language compiler that have been transformed into the .dex format by the included "dx" tool.
The Dalvik VM relies on the Linux kernel for underlying functionality such as threading and low-level memory management.

Linux Kernel

Android relies on Linux version 2.6 for core system services such as security, memory management, process management, network stack, and driver model. The kernel also acts as an abstraction layer between the hardware and the rest of the software stack.

NVIDIA Ion mini-ITX System Build Guide

DIY NVIDIA Ion mini-ITX Build

Building a mini-ITX computer system is a popular topic these days and for good reason. The form factor is very small, a wide selection of platforms is available, and the component pricing is fairly decent. This build guide will quickly go through the steps of building a mini-ITX build from out of the box to completion. Once the build is completed, I will install Windows 7 RTM and run a slew of benchmarks to see how the system performs doing some tasks that you might actually do with a mini-ITX system.  The goal of this article is to show how to build a mini-ITX HTPC system capable of playing Blu-Rays for under $600 in hardware.  Can it be done?  Easily!

Image taken from Legit Reviews
The Mini-ITX System Build Parts List:
  • ASUS AT3N7A-I Motherboard
  • Western Digital Scorpio Black 250GB 7200 RPM HDD WD2500BEKT
  • Kingston 2GB DDR2 800MHz ValueRam KVR800D2N5K2/2G
  • Panasonic UJ-135-A SATA Slimline Slot-Loading Blu-ray Player
  • Travla Mini-ITX Case C287
Before the operating system and software, which isn't that bad for what this system will be capable of doing. Once it is built and loaded up with Windows 7 RTM 64-bit for a trial run, it should be a fairly beefy system thanks to the dual-core Intel Atom Processor 330 (1M Cache, 1.60GHz, 533MHz FSB) and the NVIDIA Ion GPU.

Image taken from Legit Reviews
Many people might not understand just how small mini-ITX systems are, so here is the system that I will be showing you how to build sitting next to an early 1990's IBM 70MB ESDI hard drive. The mini-ITX system is actually just slightly larger when it comes to length and width, but is not as tall as the 70MB hard drive. The fact that the mini-ITX system on the left is loaded with a 250GB hard drive, motherboard, processor, 2GB of memory and a Blu-Ray player and is roughly the same size as hard drive from just a couple decades ago just goes to show how quickly computer components have advanced and shrunk in size.

Image taken from Legit Reviews
The Travla Mini-ITX Case C287 also dwarfs my current HTPC that was built using the Moneual LAB Black Aluminum 972B ATX media center case. The new mini-ITX system will basically cost as much as my chassis did from a couple years ago. Other than a massive space savings, this system should also use much less power.  My current HTPC uses an AMD 690G platform with a Radeon HD 4830 graphics card and consumes ~110W at idle.  The new build that I am reviewing today should idle under 25W, which is nearly an 80% reduction in power consumption.