Smartphones OSes like Android and iOS come with a lot of security features, one of the most useful to me being app isolation.
In my understanding, each app installed has a space reserved, and can only access its data.
This prevents a malicious app, or an app that gets exploited, from altering or giving away the data it isn't allowed to access.
As basically every program that accesses the Internet has flaws, why don't PC OSes provide this kind of protection ? And could one provide this without breaking compatibility with older programs ?