Journey of 4 Souls: Anybody interested to get started with Android, stay tuned.

Mobile operating systems

Android is an open source software stack for mobile devices that includes an operating system, middleware and key applications.

An open source software is available as source code , that permits the user to study, modify and improve the software.

A mobile operating system(Mobile OS) is the operating system that controls a mobile device or information appliance – similar to the operating system such as windows, Mac OS or Linux that controls a desktop , computer or Laptop.

Following are the list of few main competitors in Mobile OS

1.Android from Google Inc
2.BlackBerry OS
3.iOS from Apple
4.Symbian OS from Symbian Foundation
5.Window Mobile from Microsoft

Android

open platform http://source.android.com
can compile custom firmwares - good for hackers and other
good framework, extended on each new firmware
supports multitasking
nice IDE - Eclipse, NetBeans
development SDK is free
easy to debug, can send logs to developers
programming language is Java but bridges from other languages exist (C# .net - Mono, etc)
Android supports Java 1.5 and translates the byte code to its own custom Dalvik byte code optimized for mobile devices.
for the hardcore programmers, Android offers the possibility of programming in C using the native dev kit NDK
can run script languages like LUA, Perl, Python, etc
can install third party applications from sdcard, random sites - not strict to a specific market
applications can hook and override everything - email interface, SMS sending, custom keyboards, etc
supports widgets
can publish applications on the Android market instantly
user has access to the sdcard and can use it as a USB disk

iPhone

closed platform
no multitasking except for some Apple applications. multitasking is probably going to be introduced in the next vertion of the iPhone, the iPhone 4
development kit costs ~90E
programming language is Objective C - but bridges exist from Java, C#, etc
next version of iPhone is supposed to only allow Objective C code, you must program in Objective C if you want to create an iPhone application
applications are not allowed to duplicate the iPhone functionality - ie no custom email interface, etc
does not support widgets - unless the phone is jail broken
user does not have access to the sdcard - user can only do synchronization via internet or LAN
third party applications can only be installed from the Apple store. For testing the applications, developers can use Ad Hoc publishing
publishing on the store is a very lengthy and tiresome process. Apple has many and bizarre rules. Many applications were rejected for strange reasons.
no Adobe Flash support

Nokia

opened Symbian and says the future will be QT and WRT - they will cut support to any other environment including J2ME
QT is a framework that adds a layer of abstraction over gui, network, gps, etc.
QT is cross platform and cross programming language - C++, C#, Java, etc. the licenses are GPL and LGPL.
QT runs on Maemo, MeeGo, BlackBerry, Symbian, Android, iPhone, Windows Mobile, desktop PC, consumer electronics, car entertainment, etc
WRT - web runtime - a cool feature that allows users to write applications in HTML, JS and CS. You build the app like a normal web page, and you interact with the phone platform/hardware using the WRT bridge.
No need to learn any other technology. Just HTML, JS and CS. Very important: JS can call native code, but also the other way around. It seems you can call WRT JS with native code.
supports widgets
supports Adobe Flash Lite

BlackBerry

as it is now, the programming environment is Java native and J2ME
no Adobe Flash support yet.

Windows Mobile 6.x

native C, C# with PInvoke - not worth mentioning since MS released WM7 and broke compatibility with 6.5

Windows Mobile 7

closed platform
MS breaks compatibility with WM 6.x -
programming environment is Silverlight and XNA
no native programming ie no hooking and overriding keyboard, etc - they removed PInvoke
nice IDE - Visual Studio 2010
does not support multitasking for third party applications
third party applications can only be installed from the MS marketplace
no Adobe Flash support

Comparison Between Android OS & Other OS (Operating System)

Features	Android	iOS (Apple)	BlackBerry	Symbian
License	Open Source	Proprietary	Proprietary	Eclipse Public License
OS Family	Linux	Mac OS	Mobile OS	Mobile OS
Programmed In	C, C++ and Java	C, C++, Objective C	Java	C++