Android O - Main features of Developer Preview
Google started a new trend with Android Nougat. It launched the developer previews and beta versions before the official launch. The same is the case with Android O. Though there is no beta availability as of now. The developer preview has been made available and promises some innovative features.
In tune with the culture that began with the previous version of the Android operating system, Android Nougat, Google has made the developer preview of its new iteration of mobile operating system - The Android O. Yes, there has been no announcement on the exact naming of the latest version of the operating system. But, as has been the tradition, it will be some dessert that will begin with the alphabet O.Android N and Android O - are the previews similar?
Not exactly. Google made the Android N preview available via its beta channel. Everyone who wanted to taste the early versions of Android N was welcome to try it on their phone. The updates were available over the air. Surprisingly enough, the early beta versions were completely functional and stable. 
It isn't the case this time with Android O. No, we are not talking about the stability part. But, the preview is not available this time on the beta channel. It will be available only for the developers who own a few select devices. They will need to download the update and manually install it by flashing it on their devices.Who can get it?
As we said before, Android O preview has been named as Developer Preview and not Beta. And that should be an indication enough. The preview is not available for anyone out there.
You have to download the update from Google Developer Channel, and then flash the same manually on your phone. Non-availability through the beta program can be disappointing for the tech geeks out there. Need to flash it manually may deter some of the enthusiasts. However, there have been some unofficial leaks and reports that suggest that the update will be available on beta channel once enough data is collected from the developers.
If you are a developer and own any of the smartphones among Nexus 5X, Nexus 6P, Nexus Player, Pixel, Pixel XL or Pixel C, you can head on to the Google Developer Channel to download the developer preview . Once done, you can install it on your device by flashing it manually. Please note that no Over The Air updates will be available. What are the New Features in Android O?
Well, as the things stand as of now, there are no significant UI changes visible. It appears to be an incremental update as of now. There have been several improvements to the core system. All the predictions and explanations contained in this article would be purely subject to changes when the final and stable version is released.
Some of the major changes are
Background Limits
Google has been leaving no stone unturned to improve the battery life on its operating system. There have been consistent attempts to concentrate on improving battery life since the days of Android Marshmallow.
Google believes that apps and developers indulge in aggressive implicit broadcasting and that has been the primary cause for faster battery drain. It should be noted that Google had warned the app developers a couple of years ago that it is planning a Backgroud Process Lockdown. Android O seems to be bringing this into reality.
There have been no clear documentations available on this front, and we may need to wait to see the exact nature of these lockdowns and Automatic Limits through user reviews.
Picture in Picture
Google has always wanted to provide native platform support to some of the features launched by manufacturers on their devices. A good thought indeed - this will be helpful in avoiding monopoly of select manufacturers in select features.
Split Screen mode and Multi Window were some unique features that manufacturers like Samsung used to sell their devices like hotcakes. If that was not enough, several manufacturers have been onto the floating windows and such picture in picture concepts. This will now get official support from the operating system, thanks to Android O. Apps will now be able to get floating windows that will have their own play and pause buttons.
How does it work? You can understand by seeing what YouTube does when you press the back button while watching a video.
New Notifications
Android O is adding new notification feature. The feature is called Notification Channels. This will help apps and their developers to create bunch of notifications under individual channels.
As of now, you have been getting such features on specific apps like, for instance, on your Twitter app that lets you choose whether you want Retweets, Likes and other specific information. This feature was so far dependent on app developers and how they have been created. Settings to enable them were buried within the app.
The feature will now be supported by the OS itself. What we mean by that is the Notification Channels will now have native support.
Improved Autofill APIs
This is yet another app specific native support being introduced with Android O. We have been getting the autofill feature whenever we fill the online forms and other repetitive information that we typically enter.
You will now be able to choose a particular AutoFill app. This feature is expected to make password managers more efficient.
Better Keyboard Navigation
This is yet another improved focussed on the app developers. The feature is supposed to enable the apps to have better arrow and tab support.
We already are aware that there are several issues affecting keyboard navigation in Android Nougat, especially on Pixel phones. Since Android is usually based on a software keyboard, adding a hardware one creates issues. There have been attempts in Android O to address this problem.
Adaptive Icons
We have been seeing the concept of Adaptive icons in the manufacturer specific manner so far. Samsung has long been offering the adaptive icons in their devices. The feature will now be available in stock Android as well.
Developers will now have the options to set the adaptability so that the apps can have icons in accordance with the device.
ART optimisation
Google has gone on record stating that ART - Android Runtime - will now be faster. It has been stated that it will be two times faster on some specific benchmarks.
For the uninitiated, ART is the Java Engine that powers the apps that rely on Java on your Android phone. An improvement in ART will mean an improved performance of all apps on an Android platform. There are new Java APIs coming up too. How shall I get Android O?
If you have any of the aforesaid supported devices, you can head over to the Developers channel of Google. Visit https://developer.android.com/preview/download.html and choose the file for your device. 
You can then flash it manually on your device. Please note that this will delete all the data on your phone. We would also like to warn you that this is the first build of Android O and as such may have bugs and can also brick your phone. Proceed at your own risk.
In fact, the build is meant only for the developers, and not the general public. It will be available on Beta channel after it attains stability. Final Thoughts
Well, this is the first developer preview that has shown up. As Google works around the feedback received from the developers once they test the build on their apps, we may be able to see further features as well.
The documentation is yet to arrive. We may be in a position to find out the exact status of the update in the days to come. Till then, let us just speculate!
Follow
An update here - Google has pulled the curtains on Android Nougat Beta Program. That should be a clear indication of the fact that the next iteration of the Android eco system will be available for the public soon. We may be able to expect the Android O ( people have already been calling it Android Oreo- will that be the final name is still under wraps) beta program. Though it could still be a long way to go till the update is rolled out to the devices, you can experience it soon through beta program.