By
Tharindu Weerasinghe [MSc.Eng, BSc.Eng(Hons) – Peradeniya], the writer is a software engineer at a leading software company in Sri
Lanka.
When you travel by public
transport, when you walk along busy streets, when you are at shopping malls, or
when you are at work these days, it is not rare to see people with smartphones; in fact it is not an
exaggeration if we say “many people carry smartphones
these days”. Some youngsters try to be
smarter by using a smartphoneJ.
Many people refer smartphones to the mobile phones that have touchscreens. All
the phones that have touchscreens are smartphones but all the smartphones must
not necessarily have touchscreens.
Actually, what are
smartphones?
Smartphones are mobile phones that are
using a mobile operating system. Like the PC or laptop computer you use, these
smartphones also use an operating system to do its work. In the contemporary
world, the most famous mobile operating system is Android (by Google). There are many others too: iOS (by Apple), Symbian (by Nokia), Blackberry
(by RIM), Windows Phone (by
Microsoft) and Bada (by Samsung) are
some of the popular ones.
Many modern smartphones have high-resolution
touchscreens and web browsers that display standard web pages as well as
mobile-optimized sites (sites that are specially designed for mobile phones where
the URL starts with the prefix m.). Their high-speed data access is provided by
Wi-Fi and mobile broadband. (Source: Wikipedia)
Normal mobile phones that are
being used by us are called feature phones. There is no clear information to distinct
the two types (smart and feature). But the visible and clear significance is
that smartphones contain advanced APIs (Application Programming Interfaces) to
help them run third party applications (you call them as mobile apps). If I
elaborate more on APIs, they can be considered as mediators who act as
interfaces between different software components. – Referred: Wikipedia
Brief History of Smartphones
Since most of the modern
smartphones have touchscreens I think it is good to have some background
knowledge in touchscreen technologies:
How touchscreens work?
(Reference/Source: http://computer.howstuffworks.com/question716.htm)
There are 3 main categories of touchscreens. These 3 categories imply
the way the system identify a person’s touch.
- Resistive
- Capacitive
- Surface
acoustic wave
Resistive touchscreen system:
The resistive touchscreen system
consists of a normal glass panel covered with a conductive and a resistive metallic layer. The two
layers are kept apart by spacers. A scratch-resistant layer is placed on top of
the whole setup. An electrical current runs through the two layers while the screen
is switched ON (i.e. when the mobile phone is operational). When a user touches
the screen, the two layers make contact in that exact spot. The change in the
electrical field is noted and the coordinates of the point of contact are
calculated by the computer (here we refer the computer as hardware and malware
implementation of the mobile phone). Once the coordinates are identified by the
computer, a special driver translates the touch into something
that the mobile operating system (Android, Symbian, Windows Mobile, etc.) can
understand...
Capacitive touchscreen system:
In the capacitive touchscreen system,
a layer that stores electrical
charge is placed on the glass panel of the screen. When
a user touches the screen with a finger, some of the charge is transferred to
the user, so the charge on the capacitive layer decreases. This decrease is
measured in circuits located
at each corner of the screen. The mobile phone’s inbuilt computer calculates,
from the relative differences in charge at each corner, exactly where the touch
event took place and then relays that information to the touch-screen driver
software. In other words, the touchscreen driver software is prepared to catch
that information and send it to the mobile operating system. One advantage that
the capacitive system has over the resistive system is that it transmits almost
90% of the light from the monitor, whereas the resistive system only transmits
about 75%. This enables the capacitive system to provide a much clearer picture
than the resistive system.
Surface Acoustic Wave touchscreen system
In these systems, two transducers (one for receiving and one for sending) are
placed along the x and y axes of the screen’s glass plate.
Now you
might wonder what transducers are? Transducers are devices that convert a
signal in one form (of energy) to another form. This energy can be electrical,
mechanical, chemical, acoustic and so on. In practice, the transducers are
sensors and actuators. Sensors detect an energy parameter in one form and
report it to another form. (E.g. Heat Sensors, Pressure Sensors, Light Sensors,
etc.) Actuators, they accept energy and produce movement. (E.g. Electrical
Motors, Loudspeakers and so on)
You might
think of the term, acoustic wave. Acoustic waves are all the waves in liquids
solids and gasses including vibration, sounds and etc.
So coming
back to the 3rd type of touchscreen systems, there are reflectors on the glass; they
reflect an electrical signal sent from one transducer to the other. The
receiving transducer tells if the wave has been disturbed by a touch event at
any instant, and can locate it accordingly. So, now you might understand that
there are continuous waves (electrical signals) from the sending transducers to
another. That wave setup has no metallic layers on the screen, allowing for
100% light throughput and perfect image clarity. This makes the surface acoustic
wave system best for displaying detailed graphics (both other systems have
significant degradation in clarity).
Now
you have an idea of the touchscreens, now let us get some background knowledge
for the most widely used smartphone operating system – Android
Operating system - Android
Android is a
Linux based operating system (it uses the Linux kernel) which was initially
built by Android Inc. which was backed by Google financially and then owned by
Google. Android came to market in 2007. Android is open source and Google has
released its native code under the Apache License so that anybody can edit it
and distribute without any commercial benefit. Apache License is distributed by
Apache foundation. If you want to read it more please surf the internet.
Later versions
of Android has a Linux kernel version 3.x with middleware, libraries and APIs
written in C language and have application software running on an application
framework which includes Java-compatible libraries based on Apache Harmony
(Apache Harmony is an open source Java implementation that acts as an
application framework). Android uses the Dalvik virtual machine with just-in-time
compilation (JIT) to run Dalvik 'dex-code' (Dalvik Executable), which is
usually translated from Java bytecode. The main hardware platform
for Android is the ARM architecture. (Source: Wikipedia) If you look at the
following diagram carefully, you will get a clear picture of the Android’s
System Architecture.
Note: All the images are taken from Wikipedia.
(http://.en.wikipedia.org)
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