Android is an open source, Linux-based operating system for mobile devices like smartphones and tablets. It was developed by Google and later the Open Handset Alliance. Some key versions and features include: Android 1.5 "Cupcake" introduced the on-screen keyboard and Bluetooth support; Android 2.0-2.1 "Eclair" added near field communication and VoIP support; Android "Marshmallow" focused on improving the user experience and introduced new permissions and features like fingerprint recognition; Android 7.0 "Nougat" allowed displaying multiple apps simultaneously and added notification replies.

2. • Android is a software package and Linux based operating
system for mobile devices such as tablet computers and
smartphones.
• It is developed by Google and later the OHA (Open
Handset Alliance). Java language is mainly used to write
the android code even though other languages can be used.
• The goal of android project is to create a successful real-
world product that improves the mobile experience for end
users.

6. • Android 1.5 Cupcake was the second Android
version developed by Google, a major platform
release deployable to Android-powered handsets
starting in May 2009. The release includes new
features for users and developers, as well as
changes in the Android framework API.
• Android 1.5 included new features such as an on-
screen keyboard and Bluetooth support as well as
improvements to existing features such as UI
changes for application management and several
Google apps.

8. Android 2.0–2.1 "Eclair" is a discontinued version
of the Android mobile operating system
developed by Google. Unveiled on October 26,
2009, Android 2.1 builds upon the significant
changes made by Android 1.6 "Donut".Two major
additions in Eclair were support for near field
communication (NFC) (used in mobile payment
solutions) and session initiation protocol (SIP)
(used in VoIP internet telephony).

15. LOLLIPOP

16. Android "Marshmallow" (codenamed M in-development) is the 6th major
version of the Android operating system. First unveiled in May 2015 at
Google I/O, it was officially released in October 2015.
Marshmallow primarily focuses on improving the overall user experience of
Lollipop, introducing a new permissions architecture, new APIs for
contextual assistants (a feature notably leveraged by "Now On Tap"—a
new capability of the Google searching by contextualizing an app into a
simpler interface by Google) Now, a new power management system that
reduces background activity when a device is not being physically handled,
native support for fingerprint recognition and USB Type-C connectors, the
ability to migrate data and applications to a microSD card and use it as
primary storage, and other internal changes

17. Android 7.0 "Nougat" is the seventh major version of the
Android operating system. First released as a beta build on
March 9, 2016,] it was officially released on August 22, 2016,
with Nexus devices being the first to receive the update.
Nougat introduces notable changes to the operating system and
its development platform, including the ability to display
multiple apps on-screen at once in a split-screen view, support
for inline replies to notifications, as well as an OpenJDK-based
Java environment and support for the Vulkan graphics
rendering API, and "seamless" system updates on supported
devices

18. Reference