Newbie: Client calling a server but what CLSID

I am doing a tutorial on COM. I have created a server object (beepServer)
with ATL. I want to call that object from a client. My question is where do
I get the CLSID and the IID from? The tutorial has the following code for
the client:

const IID IID_IBeepObj =
{0x89547ECD,0x36F1,0x11D2,{0x85,0xDA,0xD7,0x43,0xB2,0x32,0x69,0x28}};

const CLSID CLSID_BeepObj =
{0x89547ECE,0x36F1,0x11D2,{0x85,0xDA,0xD7,0x43,0xB2,0x32,0x69,0x28}};
int main(int argc, char* argv[])
{
 HRESULT hr; // COM error code
 IBeepObj *IBeep; // pointer to interface
 hr = CoInitialize(0); // initialize COM
 if (SUCCEEDED(hr)) // macro to check for success
 {
  hr = CoCreateInstance(
   CLSID_BeepObj, // COM class id
   NULL, // outer unknown
   CLSCTX_INPROC_SERVER, // server INFO
   IID_IBeepObj, // interface id
   (void**)&IBeep ); // pointer to interface
  if (SUCCEEDED(hr))
  {
   hr = IBeep->Beep(800); // call method
   hr = IBeep->Release(); // release interface
  }
 }
 CoUninitialize(); // close COM
 return 0;
}

What I don't understand is where did they get the values for CLSID_BeepObj
and IID_IBeepObj. If I look in the registry I find BeepServer.BeepObj has a
CLSID of
{E3829EAD-F1BC-4ECF-B14B-687D3EC2A63D}
I think that when it compiled on my machine it would have generated a
different CLSID to what the author's had, but the format is completely
different.

I know it is probably in the manual somewhere but I can't find it.