title: How can i compute the lowest and highest possible mem addresses available from a kernel just after booting?
body: <p>After the boot up in real mode, i would like to figure out the lowest and highest
  possible memory addresses i can use. I assume i need to find out
  the actual size of the ram installed on the machine then computing
  the addresses should be simple (but just for fun, how would i do it :)). 
  Then i could use these addresses as
  the base and limit of my gdt right? That way after loading the gdt,
  going to protected mode, and setting up my segments. Ill have all the memory
  available to play with.</p>