Housekeeping operations in filters I have to implement a second order filter in DF1 or DF2. I should avoid housekeeping operations by suitable addressing strategies.

I don't understand what "housekeeping operations" means. Anyone could help me or propose a source i can find more information?

EDIT :

I use DF2 for the second-order filter:
 

As pichenettes proposes with Housekeeping the code in matlab is something like:

%x=input sample
%state=containing old input values
%compute output value
y=b(1)*x+state(2)

%Update states
state(2)=b(2)*x-a(2)*y+state(1)
state(1)=b(3)*x-a(3)*y


Without Housekeeping is going to be like:

%compute output value
y=b(1)*x+state(pointer+1);
pointer=rem(pointer+1,N-1); %increment pointer in modulo form, N number of taps 

%Update states 
state(pointer+1)=b(2)*x-a(2)*y+state(pointer+1);
pointer=rem(pointer+1,N-1);


%Overwrite oldest sum with b(N-1).x
state(pointer+1)=b(3)*x-a(3)*y;
pointer=rem(pointer+1,N-1);%Increment pointer modulo-(N-1)


Is that right?Any mistakes?
First, maybe you could give us more context (is that homework?).

I think that what is meant by "housekeeping operations" are the data transfers between registers / state variables ("delay propagation") that naturally arise when naively implementing filters. For example, a naive implementation of a 4-tap FIR would look like this:

output = h[0] * input + h[1] * x[0] + h[2] * x[1] + h[3] * x[2]
// "Housekeeping" operations
x[2] = x[1]
x[1] = x[0]
x[0] = input


The data transfers operations can be avoided on some hardware architectures (especially DSP) by using modulo addressing. I think this is what is meant by "suitable addressing strategies".