my iphone 4s crashed

by full reset, do you mean "restore" from  itunes if so i've done it and it solved the problem temporary. but it accured again.

i just wanna know why it did happen and how to prevent it??

Note: i didn't JB my phone and all my apps are legally purchased from the store.

by full reset, do you mean "restore" from  itunes if so i've done it and it solved the problem temporary. but it accured again.

i just wanna know why it did happen and how to prevent it??

Note: i didn't JB my phone and all my apps are legally purchased from the store.

i didn't get what you mean??!!!

i didn't get what you mean??!!!

He told you to check for apps running in the background. The iOS devices are not like computers, the apps do not run in the background. Just a tiny bit of Apple's apps for iOS run in the background.