How android apps download and install?

[alpha2k]

First off forgive me if things aren't worded right, I sometimes have a hard time explaining things and grasp for words to describe things correctly
Basically in layman's terms I wanna find out how the downloads work I guess is what I wanna say.
-The app downloads to the phone I am assuming, then installs from the phone storage, I am guessing at this.
-if the apps says say for instance 2.08mb, is that the size the app installs onto your phone? or will it be smaller, it seems that I have noticed the app says say 4.08mb, and I check after the install and it reads like 1.20mb big, so I am sorta confused on this, or was I just seeing things?
So if all my guessing is correct, then I have say 16mb left on my phone, an app that says it's 4mb big, should by all rights install fine without giving me the "insufficient space" nag, and go ahead and install.
I'm just exactly clear on the download and install procedures the apps and/or phone strage go and pertain to each other.
I have approximately anywhere between 16mb to 12mb of free space left on my phone, according to apps2sd anyways, so if that app is reading it correctly I should be able to still install small apps such as poweramp pro without getting the "insufficient space" nag.
I am correctly rooted, and my phone is a Samsung Galaxy Prevail. Sadly it has a very small internal storage space so that's why I am messing around with moving things to the sd card when possible, plus understanding the d/l and install process better.
I have tried the adb solution listed somewhere on here in forums where you use adb shell I guess it's called and type a line,(I forget what it is, but I have a file saved with the how to to do it somewhere), which works well and has worked for some apps, but I guess I am a really BIG widget user, so I have a lot of widgets and/or apps that can't be moved to the sd card, because they don't work otherwise, unless someone has a fairly simple solution to that, in which case I will moves quite a bit more apps/widgets to my sd card.

Thanks for any help in advance.

 

[Italo]

It depends on where you're downloading the app from. The Market stores the APKs in the system cache folder before installing. I think pretty much any other source (amazon, getjar, etc.) download to the SD card.

The file you are downloading is an install file, and won't necessarily be the same size as the app. Some of the larger apps (mostly games) have a small APK for install, then download the rest from the app.

I'm surprised you're not already getting insufficient space errors. My phone has more than 1GB left, and has told me "Low on Space" a few times now...

 

[alpha2k]

It depends on where you're downloading the app from. The Market stores the APKs in the system cache folder before installing. I think pretty much any other source (amazon, getjar, etc.) download to the SD card.

The file you are downloading is an install file, and won't necessarily be the same size as the app. Some of the larger apps (mostly games) have a small APK for install, then download the rest from the app.

I'm surprised you're not already getting insufficient space errors. My phone has more than 1GB left, and has told me "Low on Space" a few times now...

WOW! 1gb, that's amazing I have phone envy now
So since you have 1gb left that makes me think there is a different level of when the message pops up. The low level is annoying too, it gives a little notification at the top that is always there. I don't mind being notified but to be persistently at the top all the time is annoying, for me anyways.

So the app size that shows on the market isn't always the final correct size then? if not then how do you tell what size the final outcome will be on your phone, or is there even a way. I just checked winamp, it says 4.43 on the market, and on the phone according to apps2sd it says 6.53, that's 2mb difference, and in my case that's a lot of storage it's using. That's a widget I use, so moving winamp to the sd card isn't an option, because the widget stops working. I wish widgets worked from the sd card (sighs), because that would solve the problems I am having if I could move them to the sd card and they still worked.