Process, flow, differences?

Question

Android

The following phrase was said on the technostream mail ru:
The process works with isolated memory, that is, the memory areas of the processes do not intersect.
A thread uses shared memory and can change the memory available to all threads within the same process.

From what I said, I did not understand:
What is isolated memory? Is it free memory that is allocated to the application?
What is shared memory, how does a thread change the available memory? I didn't understand what that meant at all.

Answer 1

In modern operating systems, processes use virtual memory - they do not see the memory of other processes. That is, if process A has byte 0x08 at address 0x100 and process B has byte 0x42 at address 0x100, process A will always read 0x8 and process B will always read 0x42.
Each process sits in its own address space.
Threads sit inside a process and see one memory - the address space of that process. This is called sharing - once the address space is shared, then the memory is shared. If thread a in process A writes a nine to address 0x100, all other threads also count nine from there. Process B at this address will continue to read 0x42
Read on the keywords "Protected Mode," Virtual Memory ", MMU," Process "," Thread "