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I have an Android smartphone and would like to understand what is the difference between RAM, SD Card and Device Memory. When I check Memory Usage of my smartphone, I see those components:

RAM: 174 used and 52 MB free

On SD Card: 492 MB used and 3.16GB free

Device Memory: 143 MB used and 47 MB free

I understand that "SD Card" is some external memory that you put in the Smartphone. But how do I understand RAM and Device Memory?

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  1. RAM - Random Accessed Memory - When running an application on your phone, the application is loaded from your device memory into the RAM, just like on a computer, the main purpose for this is access speed is far greater in RAM. You can clear the apps that is in the RAM on your phone depending on your smartphone (Samsung for example hold home button down and click ram manager > clear RAM - this will clear what's in RAM however most background apps will automatically be loaded back into the RAM hence the free space decreasing straight away

  2. As you mentioned SD Card is a external memory card which you can switch and swap with a variety of different sizes if needed

  3. Device Memory is your phones built in memory, just like SD Card has memory however this one cannot be swapped or taken out of the phone. It will hold all of your phones files that make it work, just like a PC, as standard you cannot edit these files as they are read only, however through rooting your phone you may access these files and change if needed.

These files as mentioned take up space on your smartphone, so you may have a 16GB device memory or Device Storage, but you could actually only have 15GB free (for example not exact) to use as 1GB is used for the files I mentioned above

Hope this clear it up for you, and I'll happily provide links for further reading for you if needed

Addition Note:

Modern Android phones (4.0+) use an "emulated SD card" for their internal memory. Which means that your phone tricks the OS into seeing the internal memory as an SD card, which can cause some confusion as to the difference between SD memory and internal memory.

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    Thanks. What it's not so clear to me is RAM and Device Memory. Is RAM included in Device Memory? Or are they both independent components? – user71140 Aug 19 '14 at 15:52
  • Independent from each other. – IAmTheSquidward Aug 19 '14 at 16:07
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    @user71140 One point I would like to add is that the RAM is always dynamically occupied and freed. You may get a fixed RAM size but the occupancy is never fixed.(i.e. when no app is running it automatically gets cleared and when you are multi-tasking It gets filled) also you will never find 0 RAM occupied because in Android always some or the other app is running in the background. – user285oo6 Aug 20 '14 at 6:50
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    @user285oo6 The RAM is your brain, taking in information always working, always doing something. The device memory is like a book, it stores the information that isn't needed immediately as part of the phone executing code. It's a silly analogy but just think of RAM as a few little chips that handle what is actually happening on your phone, and device memory is basically a hard drive that stores things long term. So you click on an app, the app is stored on your device memory, the phone loads it (or part) into RAM and starts it running, the CPU crunches the numbers. – RossC Aug 20 '14 at 12:10
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I had the same question, and I found this answer to be helpful. The short summary is that "device memory", AKA "internal storage", is non-volatile: in other words it's persistent across device reboots, unlike RAM.

Internal storage is flash memory, similar to a solid-state drive or a microSD card. One way to look at it is that device memory and a microSD card use (practically) the same technology, just that the microSD card is removable.

Flash memory is much slower than RAM, and has to be written in large chunks, unlike RAM. Its role would be more like that of a hard drive than like RAM.

protected by Community Oct 20 '15 at 23:48

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