MOBILE OPERATING SYSTEMS
Just as the programs on your desktop or laptop computer need an operating system to run on, the mobile apps that run on devices such as phones and tablets also require an operating system to run on.
Mobile device operating systems share several basic characteristics with the traditional desktop based operating systems. For e.g. both kinds of operating systems can launch software programs, execute the binary instructions of the programs on the microprocessor and on other specialized kinds of processors such as the graphics processor, manage CPU usage and RAM usage among different programs, manage peripherals such as the screen, external USB memory, keyboard (the on-screen version of it), and manage wireless network connections such as WiFi, Bluetooth etc.
That said, mobile device operating systems differ in their operation from traditional desktop operating systems in a few fundamental ways.
Figure 75: Graphic illustrating the unique features of mobile operating systems
The most important area in which mobile operating systems differ from their desktop cousins is in the ability to effectively manage the primary function that a mobile phone should perform, namely, the telephone function. Mobile device operating systems are designed to give maximum priority to the phone program on the device. No matter what else is running on the device, an incoming or outgoing phone call or SMS is given the absolute top priority, sometimes at the expense of completely terminating an app that the user is running.
Another area where mobile operating systems differ from desktop operating systems is the strict control that the former maintain over the lifecycle of a mobile application. It is not unusual for a mobile OS to preemptively shut down an app that is in the background and which is consuming too much RAM. In fact, several well designed mobile SDKs such as the Apple iOS SDK and Google Android SDK provide specific callback methods for the programmer to implement in order to do cleanup or data save operations right before the OS terminates the app.
A third significant difference is the type of processor hardware (or the chipset as it’s called) that the OS runs on. A desktop OS such as Microsoft Windows runs on what is known as the x86 CPU architecture pioneered by Intel. Apple Macs used to run on Motorola 68000 family processors and later switched to the Apple Power PC chipset before finally transitioning to Intel’s x86 processors in 2006.
Mobile operating systems run on processor architectures such as the ARM architecture designed by the British company ARM Holdings or on Qualcomm’s Snapdragon processor architecture. Incidentally, the Snapdragon architecture has many similarities with the ARM architecture. Today, there are more than a hundred chip manufacturers such as Broadcom, Texas Instruments, Samsung and many others that are licensed by ARM Ltd to manufacture ARM architecture based mobile chipsets. These processor architectures were designed with specific goals such as achieving ultra-low power consumption and high multimedia performance.