Computing a time it takes for matlab to complete a nest of for loops?

I'm trying to calculate the time it takes for matlab to complete three nests of for loops each going from 1 to a hundred. I used cputime to calculate the time. Problem is, the time increases in each trial I make. My code goes like this:

 t=cputime;

 for i = 1:100
     for j = 1:100
         for k = 1:100
         end
     end
 end

 t

Nothing should be running in the loop. I am required to just take the time it takes for matlab to go through all of the loops.

Answer 1

[Azzi Abdelmalek]

Use tic toc

tic
for i = 1:100
   for j = 1:100
       for k = 1:100
       end
   end
end
tim=toc

[Azzi Abdelmalek]

When you say nothing should be running in the loop, it's false, the incrementation inside a loop can't be done without Matlab running!