Develop Reference

What is difference between Android and Android Rom?

I am new to AOSP anybody tell me what is difference between Android & Android Rom
I have found when i am googled but I did not understand the exact difference
Android is the open-source operating system used for smartphones.
Android ROM is the Android operating system. It is composed of a Linux kernel and various add-ons to achieve specific functionality.

As far as I know:
ROM
Literally it stands for Read Only Memory. When people talking about ROM it`s referring to the phone's internal memory. The memory where your firmware/apps are stored. When people say, falshing a new ROM, it means they are flashing a new version of the firmware onto their phone.
Android
In this case they are referring to the OS or to the product of Google.
Brace your self, Obvious link coming:
https://en.wikipedia.org/wiki/Android_(operating_system)

ROM is in fact "Read Only Memory." But for your purposes that has nothing to do with the use case here. Early on with some hardware the operating system was stored on a specific chip, a ROM chip. What you flashed onto that chip is called "the ROM image." It had to be written with special purpose hardware, or it had to be written to in a special boot sequence (like with a DOS bootdisk).
With Android, we distribute images which usually overwrite a file system without formatting it or partitioning it. That's more of a sloppy and crappy install and it's likely to go away at some point in time when someone clever does it the same way a desktop runs. So an "Android ROM" is usually just like a zip archive that gets unzipped to /. That's a bad way to upgrade a computer, but it's how it's done for now. It's also more acceptable to do it in such a bad way because on phones upgrades are done so seldom. You may get an OTA upgrade once a month, or every other month. And, you likely upgrade your phone fewer than 10 times.

How to modifiy the system apps running on my phone

I want to modify the system apps running on my specific phone. I am stumped about some important steps on how to do that - see my questions further below.
N.B.: I am not interested in deploying these modifications to other phones. Instead I want to play with the original code and improve it. Hence "create your own system app" is no sufficient answer.
Background
I am just starting to get into Android development (have sufficient Java knowledge, though). There are plenty of great tutorials out there (e.g. here and here) but they all seem to cover user application development. I'm more interested in getting (a little) "closer to the metal". Unfortunately I am unable to find good sources teaching how to do that.
Example
As an example let's say I want to modify how the built-in brightness control works (e.g. changing the minimum) or want to add features to the call screen (e.g. "Send SMS instead" when the line is busy).
Specific Questions
I obviously need these things to get started...
Sources
The sources for (parts of?) the OS running on my phone. This is the part that confuses me the most. Can I just download the official sources or is it likely that my vendor made modifications?
In my specific scenario (I use a Fairphone), could those modifications be contained in any of these sources:
some core apps deployed by the vendor
the image binaries (some way down the page)
sources for the Linux kernel and some other libraries
Tools
I really hope to stay in Java-land. But either case I need a development (I hope to use Android Studio or Eclipse ADT) and a debugging environment (I hope the Android Virtual Devices suffice).
Is it a valid assumption that I can use those tools for system apps or are they usually implemented in C?
Process
Assuming I can download the official sources and get started with, e.g. Android Studio. As opposed to developing a user app, do I have to do anything special to emulate the modified system app on AVD?
I'm asking because I assume that AVD already runs an unmodified version of that very app.

I am just starting to get into Android development (have sufficient Java knowledge, though). ... I'm more interested in getting (a little) "closer to the metal".
You can of course follow your own bliss, but you may find it pretty frustrating to learn Android development by hacking on the OS itself. You'll find yourself doing a lot of OS debugging and working with harder-to-use tools than normal.
Example
As an example let's say I want to modify how the built-in brightness control works (e.g. changing the minimum)
I realize this is just an example, but this could be a tough one, because there are a lot of things that contribute to brightness control -- there's the app with the UI that sets it, but that talks to the framework and ultimately the driver for the hardware that actually deals with brightness curves for the display, in coordination with the ambient light sensor.
or want to add features to the call screen (e.g. "Send SMS instead" when the line is busy).
There's a dialer app, but implementing a feature like that will be...difficult, provided it's even feasible. I don't know offhand whether that sort of call state is available to the API.
Specific Questions
I obviously need these things to get started...
Sources
The sources for (parts of?) the OS running on my phone. This is the part that confuses me the most. Can I just download the official sources or is it likely that my vendor made modifications?
If you're replacing system apps, you'll need to run an OS signed with debug keys; you don't have access to the signing keys for the installed system apps on a retail build of the OS that would enable you to replace them. That will mean either getting a debug-keys installation or building it yourself from source, and flashing it to your phone. I would most strongly discourage you from using your daily phone for this sort of work -- you don't want it to be bricked when you need to receive an important call.
If you're not running a Nexus phone, then yes, your vendor has made modifications. The system apps are probably modified, and you almost certainly won't have access to the closed source of those apps. Also, there will be closed-source device drivers that are essential to the operation of the OS that you won't have access to. If you're trying to get AOSP Android up and running on such a device, as an individual hacker it's at best very, very difficult. If you're willing to use something like CyanogenMod, you could look to see if (and to what extent) they support your hardware.
If you are running a Nexus phone, then it's a goal of the AOSP project to try to have the OS bootable on select Nexus devices, though you won't necessarily enjoy the fullest functionality of the retail OS build, depending on the state of drivers -- even Nexus phones can have closed-source drivers and bits that make life more, um, exciting for building with AOSP.
In my specific scenario (I use a Fairphone), could those modifications be contained in any of these sources:
some core apps deployed by the vendor
Almost certainly
the image binaries (some way down the page)
Not sure what you mean by that
sources for the Linux kernel and some other libraries
It's unlikely there are significant modifications to the kernel itself, though vendors sometimes do...interesting...things with system configuration. I already mentioned device drivers. Vendors also have custom implementations/modifications of some framework APIs.
Tools
Vendor-specific tools are rare.
I really hope to stay in Java-land. But either case I need a development (I hope to use Android Studio or Eclipse ADT) and a debugging environment (I hope the Android Virtual Devices suffice).
Much of what you want to do can probably be implemented in Java, though it depends on how close you're getting to the hardware which can be difficult to know.
Is it a valid assumption that I can use those tools for system apps or are they usually implemented in C?
The "system apps" are implemented in Java, but again, you sort of have to know where the dividing line is.
Process
Assuming I can download the official sources and get started with, e.g. Android Studio. As opposed to developing a user app, do I have to do anything special to emulate the modified system app on AVD?
That's actually different, because you're dealing with an emulator system image instead of a phone image. The emulator system images are completely open source, and you can build them from AOSP.
I'm asking because I assume that AVD already runs an unmodified version of that very app.
That's correct.
To come back to my initial point, if you read between the lines of what I'm saying, I won't tell you it's impossible, but the difficulty ranges from freakin' tough on the easy end to spend-years-of-your-life on the hard end. If you really want to proceed, your best bet may be to buy the phone that's best supported by CyanogenMod and work that angle; there's a more active developer community there to help you. I know you're more excited about trying to customize the OS than you are in making a user-space app, but you'll experience less frustration with the latter than the former.

How can I kill everything on my Android tablet except my app, and keep them all dead?

Please don't tell me what a bad idea this is. I am not using it as an Android tablet. It is the interface for a propitiatory medical system my company is designing. It's only function ever will be to control the system we are building.
That being said, how can I remove everything from the tablet and only run my app until the tablet dies or the standard firmware is reinstalled?
The tablet is being used exclusively as an interface control panel and CPU to my program which controls the medical equipment externally. I don't want anything else on the tablet. I don't want the users to do anything other than run my program on my equipment.
How can I lock the users into only using my program for the life of the tablet?
(I am building a system that happens to use an Android tablet to control it. Basically, I thought it would be easier to use a tablet, rather than design from scratch a system based on one or more microprocessors and which uses a custom designed and built color interface panel. If the doctors want to use an Android tablet for their offices, they are welcome to buy one.)
Thank you in advance.
Thank you all for your advice.

You will have to build your own version of Android if you wish to do this. For several reasons it is not possible to make an application that will do what you want and have it work on consumer devices.
Exactly how you need to go about customizing the OS build is going to depend on your exact hardware. But the simplest modifications will be removing the unneeded apk files from system/app/ and data/app/
AOSP and XDA-Developers are two great resources for learning the ins and outs of building a custom ROM.

If the device has reasonable power to it, you shouldn't need to worry about background processes.
If this is a consumer product, then it probably has the Google Apps suite and other related items, in which case rooting it and not installing those would be the best route. AOSP only runs processes that it needs to run Android out of the box.
Edit: You might just write the apps a Launcher and not allow opening other apps as the best route to accomplishing your goals.

You might need a custom ROM. It really depends on what version of Android your device supports. Check out the last in the list below.
http://www.redmondpie.com/best-most-popular-custom-roms-for-android-and-why-you-should-try-them-out/

I'm facing similar obstacles utilizing my business tablets. I want to restrict all the pre-loaded applications & only allow the tablet to be utilized for certain applications. White listed websites & such. I wonder if a 3rd party service such as ZENPRISE might offer a mobile management system that would take care of this for me?
zenprise

Is it possible to run R from a tablet using Honeycomb (Android 3.0)?

I have a Xoom tablet and it would be great if I could run statistical analysis using R on it. As far as I know it is not possible to use R on iPad due to license problems (GPl x iTunes etc.) and a lack of compiler for Fortran in the Apple tablet.
But what about tablets using android? Arguably, the GPL issue is not a problem, so any help here on how to use R on my tablet?

I used Linux Installer from http://android.galoula.com/en/LinuxInstall/ (my Dezire Z was rooted beforehand), installed stable debian and R! on this Linux install. I`m not a Linux-geek and total time for installation (first time loop file size was insufficient, and I repeated the whole process) wass less than hour however.
(source: gyazo.com)

At some point, smartphones and tablets will have browsers capable enough to run RStudio in its server mode via the browser. Currently, the latter demands too much in terms of newer GWT, Javascricpt, ... magic that it remains limited to (recent enough) desktop browsers; see here for a bit more on this.
You can always ssh out though. Connectbot is a capable ssh client for Android, and of course free. No graphs though.

The Android SDK offers developers the facility to program in Java, ... not C or Fortran, which are the languages in which R is written. Although some have said that hacking the Android tablets voids their warranty and prevents upgrades, Motorola only requires that the device be relocked before doing upgrades. For this question I think it still boils down to "if you have to ask the question, then you cannot do it".
EDIT: But somebody else will probably try it.
(I haven't found gcc for the Android.)

Build android system from source

I've recently purchased Samsung Galaxy Android phone after using Openmoko phone for 2 years.
One of the reasons for choosing Android was is that it's open sourced.
I don't want to depend on phone maker to provide updates for my phone. I'd like to do it myself.
Right now I'm in research stage if it's worth the time or not. So here are the questions:
I found some tutorials for building ROM images from source. They tell that Android build script will ask for make of the phone before building kernel. Does it mean that all the phone specific stuff is handled by the script or I will have to do some voodoo before I can flash it onto my phone?
Drivers. How are they handled? Are they included in the source as binaries and added automatically (question 1) or will I have to dissect old firmware to get them and put in my build? I realize that would mean some problems with module/kernel versions compatibility.
Is there is something I'm not aware of that would prevent me from building my custom firmware or make it very time-consuming?
I'm not afraid of installing SDK's and toolchains, after all I'm an Openmoko owner.

It's gonna be a little more complicated than that.
On any consumer Android phones I've seen, the user doesn't have root access to the OS. So step one, would be finding an exploit to get root.
Even after you get root, all consumer Android phones "lock" the bootloader to prevent unauthorized OS images from being booted.
The Android OpenSource project only contains device drivers for a small number of phones (Google dev phones, possibly the Nexus One?). For other phones, the drivers are proprietary binaries that the manufacturer loads on the phone. They generally aren't available separately.
Even with all of those obstacles, some enterprising smart guys have managed to create custom "ROM's" that blend the OpenSource release with drivers ripped OEM install on the phone, etc. CyanogenMod is one of the best known and is available for several different Android devices, but unfortunately the Samsung Galaxy does not currently appear to be one of the device supported by Cyanogen.
I found an old link here to a guide to getting root on the Galaxy and loading a custom ROM on it, but unfortunately the ROM they link to doesn't seem to be actively maintained anymore. It might be worth doing some more exhaustive google searches to see if you can find anyone doing active development on the Galaxy.