Operating systems with support for memory protection and virtual memory generally don't behave that way for security reasons. Everything that is allocated to a

Operating systems with support for memory protection and virtual memory generally don't behave that way for security reasons. Everything that is allocated to a process will be zeroed explicitly or on first reference. There are older operating systems that don't do that though. On the Amiga you have to explicitly ask the OS for memory to be cleared, and if you don't you may get uncleared memory left over from some other process.