Re: i have too much memory but could not download any thing in Micromax A120
Internal memory (that's where downloads go) is partitioned into a few different areas - differently on different phones. According to the specs, you should have a total of 4GB or internal storage, most of it used by Android, so you can't load many apps on that phone.
If you want more space, get a large microUSB card (I recommend SanDisk - they cost a little more, but if you ever have a problem [the only one I ever had - and I've been buying their products since before they were called SanDisk - was a microSD card I broke by being clumsy], they're a web browser away - you do a live chat, they give you instructions and they replace the card if they can't get it working online by telling you to do things) it's worth the few bucks. Your phone can support up to 32GB. Then run
External 2 Internal SD (Root) (you have to be rooted, whether you run the app or change the file by hand if you understand Linux) and your 'internal' storage for apps is your external SD card. (You can use your current card - it looks as if you're probably using a 16GB card.)
If you do this,
MAKE CERTAIN that you always keep a current backup of everything (see
Backing up an Android Device) - SD cards don't use the same technology as the internal storage does, and constantly writing to them (which the phone does) can cause a failure sooner than you want to replace the phone. If everything is backed up, it's just a new card and a couple of hours of work. If you're not backed up it's goodbye pictures, songs, videos, etc. (Keep a copy of the entire backup in the cloud - Mega gives you 50GB free - so even if your phone and hard drive go bad at the same time, you still have a backup. [If the Eastern hemisphere (Mega is in New Zealand) "goes bad" you'll have bigger problems than backups - like breathing vacuum.])