What Is Multitasking in Smartphones?

Understanding how multitasking works on the iPhone and Android

A multitasking operating system can run more than one program or app simultaneously. To do so, the OS must diligently manage how instructions and processes are handled in the microprocessor, and how their data is stored in main memory. There's multitasking on iPhone and Android smartphones, but it doesn't work the same way as on computers.

Multitasking in Smartphones

Apps in smartphones that run in the background do not always necessarily display multitasking. They can, in fact, be in three states: running, suspended (sleeping), or closed.

When an app is in the running state, it is in the foreground and you are using or interacting with it. When an app is running, it works more or less like apps do on computers, i.e. its instructions are being executed by the processor as it consumes space in memory. If it is a network app, it can receive and send data.

Most of the time, apps on smartphones are in the suspended (sleeping) state. This means that they are frozen where you left it; the app is no longer being executed in the processor and the place it occupies is in the memory. In this case, the data it holds in memory is temporarily stored on secondary storage (SD card or phone’s extended memory—analogous to the hard disk on a computer).

When you resume the app, it returns you to where you left off, rescheduling its instructions to be executed by the processor and bringing back the hibernating data from secondary storage to main memory.

Multitasking and Battery Life

A sleeping app consumes no processor power or memory, accepts no connection, and consumes no additional battery power. This is why most apps for smartphones adopt the sleeping mode while asked to run in the background; they save battery power.

However, apps that require a constant connection, like VoIP apps, should be kept in the running state, which drains battery. This is because if they are sent to sleep, connections will be refused, calls will be declined, and callers will be notified that the recipient is unreachable.

Some apps have to run in the background, performing real multitasking, like music apps, location-related apps, network-related apps, push notification apps, and especially VoIP apps.

Multitasking in the iPhone and iPad

It started in iOS with version 4. You can leave the running app and switch to a background app by going back to the home screen. Notice here that it is different from closing an app. If you want to resume with an app in the background, you can use the App Switcher, by double-pressing the home button. This will bring the focus to an array of app icons currently in use while blurring out the main menu. The icons that appear are those "left open." You can then swipe to run through the whole list and select any one of them.

iOS also uses push notifications, which accept signals from servers to awaken apps running in the background. Apps receiving push notifications cannot go to sleep completely because they need to remain in the running state to accept incoming messages. You can choose to "kill" apps in the background by using the long press.

Multitasking in Android

In versions of Android prior to Ice Cream Sandwich 4.0, pressing the home button brings a running app to the background, and long-pressing the home button brings up a list of recently used apps. Ice Cream Sandwich 4.0 changed things a bit.

There is a prominent recent app list which gives you the impression of managing the apps, but that's not the case. Not all apps in the recent list are running—some are sleeping and some are already closed. Tapping and selecting one app in the list might spring up from an already running state, or it might wake from a sleeping state, or load the app afresh.

Apps Designed for Multitasking

Some apps are designed to work in a multitasking environment. An example is Skype for iOS, which has new capabilities for handling notifications and remaining active in the background while using minimal battery power. Skype is a VoIP app that allows voice and video calls, and therefore needs to remain active always for better user experience. This works much like your mobile phone, which is always checking for signals from incoming calls and text messages.

Some users want to disable multitasking on their devices, probably because they find that apps running in the background slow down their machines and consume battery life. This is possible, but operating systems do not actually give easy options to do that. For iOS, it may even require jailbreaking the phone.

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