R help - Sep 2004 - How the residuals are calculated in a fitted ARCH(1) model.

I have used garch in package tseries to fit an ARCH(1)
model
   X_{t} = sigma_{t} e_{t}, where e_{t} ~ N(0,1)
   sigma_{t}^2 = b0 + b1*X_{t-1}^2 
 
to a set of data.


Can anyone please tell me  how the residuals are
calculated.
At first I thought the residuals are the usual
residuals
when  we do linear regression X_{t}^2 on X_{t-1}^2.  

Thanks in advance for your assistance !




====Home page :
  http://uk.geocities.com/matmsh/index.html