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iOS - Process Management - Rishabh, Saumil, Richa

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Rishabh Bidya

on 24 September 2013

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Transcript of iOS - Process Management - Rishabh, Saumil, Richa

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iOS - Process Management - Rishabh, Saumil, Richa

The iOS is one of the most preferred Operating Systems for smartphones and tablets due to Apple’s unique approach in managing processes and memory, especially in cases of web running devices.

A fact supporting conclusion :
By the end of 2012, iOS had a 21% market share of smartphone mobile OS units, but ..
It accounted for 65% of mobile web data consumption.

iOS - Process Management - Rishabh, Saumil, Richa

Stands for Automatic Reference Counting.
Instead of having to add in separate blocks of code to count references and deallocate memory, ARC handles it.
Performs in a way similar to garbage collection, however allows manual memory management too.
Compiler examines a code and adds a retain or release message in the compiled code.

iOS - Process Management - Rishabh, Saumil, Richa

Each process in iOS is made up of one or more threads.
Each thread represents a single path of execution.
Each application starts with a single thread, which runs the application’s main function.
When an application spawns a new thread, that thread becomes an independent entity inside the application’s process space.
Threads inside an application share the same virtual memory space and have the same access rights as the process itself.

iOS - Process Management - Rishabh, Saumil, Richa

Layers in iOS

iOS is divided into four abstraction layers, viz : Core OS layer, Core Services layer, Media layer, Cocoa touch layer.

Core OS layer contains low level features on which other technologies in iOS are built upon.
Manages Concurrency, Networking, File System Access, Standard I/O, Memory allocation, Math computations.

Core Services layer contains fundamental system services for apps.
Manages iCloud Storage, ARC, Data, Foundation, location, media, event kit, Safari services and other frameworks.

Media layer contains graphics, audio and video technologies to implement multimedia experiences.

Cocoa touch layer provides frameworks for managing touch based inputs and UI services.

iOS - Process Management - Rishabh, Saumil, Richa

Multitasking in iOS

Starting with iOS 4, multitasking is supported through seven different APIs, viz:
Background Audio, Voice Over IP, Background location, Push Notification, Local Notification, Task completion, Fast App Switching.

In iOS 5, three new background APIs introduced: Newsstand , External Accessory, Bluetooth Accessory.

In iOS 7, Apple provided all apps the ability to perform background apps.
It prefers to update user’s most frequently used apps.
Prefers to use wifi network over a cellular network, without markedly reducing device’s battery life.

iOS - Process Management - Rishabh, Saumil, Richa

What is iOS?

Runs on the XNU kernel
XNU is a hybrid kernel.
XNU stands for X is not Unix.
Contains features of both monolithic and microlithic kernels.
Message passing ability of microkernels enables greater modularity.
Retains the speed of monolithic kernels for critical tasks.
Is programmed in C, C++ and Objective C.

iOS - Process Management - Rishabh, Saumil, Richa

iOS – A short introduction

iOS (Originally iPhone OS) is a mobile operating system developed and distributed by Apple inc.
Originally unveiled in 2007 for iPhone, it has been extended to support iPad, iPad Touch, Apple TV, etc.
Derived from OS X, used on Apple Computers.
The current release, iOS 7 was released in September 2013.

iOS - Process Management - Rishabh, Saumil, Richa




iOS - Process Management - Rishabh, Saumil, Richa

Activities in iOS - Signals

An activity in iOS is what controls an application.
Activities initiate actions in applications resulting in a change of state.
The entry points of applications are always signals.
The signals are defined using C functions.
Whenever an application starts, the previously running applications are moved to background.
The signals are defined in a way that the previously running applications are mostly paused. However some applications like Safari or image viewers remain active in the background.

iOS - Process Management - Rishabh, Saumil, Richa

Processes in iOS – The Ground Level

Every Application is a process in itself.
Every Application (so called Apps) acts as a monolithic kernel.
Has a separate block of memory allocated to it.
Every block has a predefined lower limit for memory usage.
Every application has only one entry point. This point gets activated on the basis of touch input or by other applications.
If the user plays music, the entry point gets activated by the user’s chosen input.
If data backup is made, or OS updated are done, iTunes provides the inputs to the entry points.
The applications communicate using the standard URL scheme.

iOS - Process Management - Rishabh, Saumil, Richa

Process Management - iOS

-A work by

Saumil Shukla (13030142021)
Richa Mishra (13030142005)
Rishabh Bidya (13030142039)
- MSC CA (Year- I)(B Div)

How are threads used
Memory Management in iOS through ARC
Conclusion :
Full transcript