Program address range

Program address range

When I write a simple program using C / C++ , what's the address range I
get? I mean, I can point to wherever I want.. like :
void* ptr = (int*)0xFFFFFFFF;
Where does that pointer actually point to? I guess its not the real
address in the main memory but just the "cover" address of my program.
Can anyone explain that to me? What's the address range I get (in windows
for example) when running my own C program? Can I really access other
program's address range if I want to?
Thanks!