Apps Memory Reallocation of the Android OS

[appleaj]

From what I've read on these forums, Android only uses what programs are necessary and that the other programs, while taking memory, aren't hurting battery life or utilizing the CPU. So therefore, the task killers are useless and only cause more battery usage by causing the need to restart these programs.

So my question is to those who understand memory allocation, what happens when you run out of memory? What priorities does Android go by?

 

[Deleted User]

Empty processes go first (basically just memory kept around to improve app start-up times)
Background processes go second (such as an app that has been stopped and has no threads assigned to it)
Service processes go third (a running service that has not had its priority raised)
Visible processes goes fourth (typically this is a process that has another activity partly obscuring it)
and the active process goes last (the one the user is interacting with)