Memory addresses.

[Atheist]

Hey.
I was in a lecture today about pointers, in C.
It got me pretty interested, so I figured it'd be interesting to go through all memory addresses on a computer and retrieve its value. I ran into a few problems and well..here I am to try and clear my confusion:

1. Is the first memory address 65536 (0x00010000)? If so, why? Why not just 0?
2. How do I know the last memory address?
3. When I try to read some memory addresses I get this error:
   
   Attempted to read or write protected memory. This is often an indication that other memory is corrupt.
   
   Why are certain memory addresses 'protected'?
4. Is what I'm trying to do even remotly possible?

[timeshifter]

The protected memory issue should be a no-brainer for you. Remember the apps I've written in C# lately? What happens if you try to hit memory in use by the app while it's working? I lock it down to ensure that 1) it doesn't go anywhere, and 2) that nothing gets changed on me.

[Davadvice]

memories, ahh this takes me back about 7-8 years.

I found this very intresting untill it got complicated and i lost intrest with the guy trying to teach me.

I believe the answer to your question is as TS stated it is protected to prevent the application that is using it encoutering Errors and to ensure a degree of security i would imagine. It means that anouther applicaiton can use that address as it is in use.

I think there is an app that comes with VS6.0 called SPY++ that allows you to look at the memory used by a running application, this may be a good tool to understand what is going on.

Normaly when i see questions on this it's another noob looking to hack a game, because they can't play it legit.

David

[Atheist]

Yeah I know that topics like these have become "taboo" because of dirty little hackers. Its a shame though because its really interesting technology. Personally Im just interested in how these things work.

I figured that applications could in some way lock memory addresses, but the last sentence in the error message confuses me:
This is often an indication that other memory is corrupt.

Im also still very curious about question 1,2 and 4

[jmcilhinney]

If you get that error message you are reading memory you shouldn't be. If your code is written properly and you're not being malicious then the only reason that that would happen is if some other memory was corrupt, thereby telling your app to access the wrong memory address.