[Galaxy S III Android Development] xda_Noob.:
Well I can't explain it very well because of lack of English but i found wonderfull description through google and that explains exacly the same as i would like to explain you:

Warning Long Text:

Why is unused RAM wasted RAM ?

Android, like Mac OS and Ubuntu, wants to use all the RAM it can, because that's how it was designed to work. There are settings (in Android we call them "minfree" settings) to tell the system how much RAM to leave free and available, but the rest is designed to fill up as fast as possible and stay that way.

You're probably thinking "What's it filling up with?" That's a great question. After the system, graphics, radios, and any other tweaks to RAM are done loading, the rest is there to load apps into memory, right up to the point where the OS says to stop. Load the app as it's being used, and keep it there for the next time until it needs flushed to free space for something else. The more you use the system, the better it gets at keeping the right things loaded and ready to go. Think about how you use your phone -- you might have 100 apps installed, but there are a few you always are opening and using. Eventually, most of those apps will be stored in your RAM, simply because you're always opening them and loading them into the RAM if they weren't already there -- and "erasing" other apps that were there first. Loading an app from your storage takes longer, is harder on the battery, and overall worse than loading it from it's cached position in RAM.

Consider this -- Jerry did/said/thought something that made his wife mad (yes, she can read my thoughts), so he bought flowers from the 7-Eleven and wants to make a mix CD of her favorite Rod Stewart songs to give to her and get his ass out of the doghouse. It could happen. Consider which is more efficient:

Burn 20 songs to a CD, give to wife, and smile while she plays it.

Burn one song to a CD, let her listen, then erase it and burn the next song.

That's what your phone (or tablet) has to consider. Loading Google Talk to RAM once, and having it there to open almost instantly is far better than loading it each and every time you want to use it. So why kill it off? It's not like you'll never use it again, and nothing else is going to use that RAM while it's sitting empty -- at that point, it's wasted space. You will also use a lot more battery power re-opening Talk every time you get a message than you will by having the zeros held as ones on your RAM. The folks who built Android really did know what they were doing when it comes to memory management. After the parameters are set, and the amount the OS can use to "swap" for it's normal operations, the rest is simply wasted if we're not using it. What is cached in RAM is just sitting there, not using any CPU cycles, but ready to get pushed to the front and appear on the screen as fast as it can, and not use the extra battery needed to start it up from disk again.

But my Phone Runs better if I clear RAM

Having 4MB of RAM made old Windows 3.1 computers better, too. Android, and the hardware it runs on, evolves in our hands -- it gets better with every new release. The software is better, the hardware is better, and the folks writing the apps are getting better at it with better tools. We're going to use the HTC Hero as an example here, because we don't talk about the HTC Hero enough anymore.

By today's standards, the hardware and the software on the Hero suck. It sucked the same when it was new, but at the time we didn't have Bionic's or Thrill 4G's to compare it to. We only knew that there were three ways to make it run faster -- yank HTC Sense off of it, use a task killer, or tweak the system a whole helluva lot. Two of those options need root access -- so that puts 90+ percent of users out of the picture.

Normal people don't root their phones, and Harriet Housewife (or Tommy Textgod) are normal. They bought a phone that could do more than any other phone they ever used before, so they tried to do it all. Android and HTC Sense weren't near as good at managing themselves and their memory needs back then, and having the RAM full meant that there wasn't quite enough left over to run the user interface as fast as it did when the RAM was empty. Hackers soon found that tweaking the existing settings that decide how much RAM to keep free did a wonderful job at fixing that issue, and we all were happy. But if you didn't want to hack your phone, you had the option of just living with it being slow every once in a while or using a task killer to free up some RAM. I'll bet most people just lived with it (the number of people who installed a task killer is waaayyy smaller than the number of people who bought an old Hero, Eris, Cliq, or Behold), but people who spent any time on the Internet fell victim to the lure of a task killer. Soon, forums across the web filled with tales of woe about things not working right -- because everyone was randomly killing off important system processes and apps that needed to stay running.

There were also issues with apps. A correctly coded app that uses a ton of resources, let's say Plants vs. Zombies, gobbles up a bunch of your RAM while you're using it, but gracefully exits and purges itself when it's done. That means the RAM is free, being wasted, and needs filled up again when you load up Google Talk. When you're done chatting, Google Talk just gets sent to the background because it didn't have to take a ton of RAM and should stay loaded for the next time. When Android was shiny and new, a lot of apps that used an excessive amount of system resources didn't exit gracefully, and the OS struggled to purge RAM and load itself back to the foreground -- causing lag when you closed a big app. Sometimes the lag lasted a while, and people soon tired of it. Killing every damn process you can and jacking the free RAM up as high as possible, or even worse -- scheduling a task killer app to do it automatically every so often -- seemed like the best solution to a whole lot of people. We're mostly past that now. App developers are crafty, and the tools they have at their disposal mean that most of the time they get it right -- even on the first try.

For more see:

http://www.androidcentral.com/ram-what-it-how-its-used-and-why-you-shouldnt-care

---------- Post added at 03:26 PM ---------- Previous post was at 03:18 PM ----------

I qoutet you because I want to teach you about RAM and you replied the person. Dont't blame me, it was just an reply to the RAM topic.

Anyways don't wanna make you angry Sorry !