>> unitround
After   53 iterations of while loop, we find
  unitroundoff =   2.220446e-16 
%
% matlab provides this value through the variable "eps"
help eps

 EPS    Floating point relative accuracy.
    EPS returns the distance from 1.0 to the next largest
    floating point number. EPS is used as a default tolerance by
    PINV and RANK, as well as several other MATLAB functions.
 
    See also REALMAX, REALMIN.

% and we can see this value without computing our own
% version in the while loop above by simply printing it
% out by given the variables name on the MATLAB command line
format short e
eps

ans =

   2.2204e-16

>> type unitround

% unitround.m
% k stewart - spring 1998 - written for CS 205
% We will compute the Unit Round Off - now that we have a
% feeling for how the "arithmetic" works
%

u = 1.0;  % need to start somewhere - why not at 1.0?

% count how many times we go through this loop

count = 0;
while (1.0 + u > 1.0),
    count = count + 1;  % in c, you could simplify to  count += 1;
    ubig = u; % u still changed 1.0, so keep track of that value in ubig
    u = u/2.0;
end;

% we now have the first value of u so that 1.0+u <= 1.0, although
% we were searching for the value that DID change 1.0, so
% that occurred in the iteration right before the loop exit
%
% after running the "while" loop

fprintf('After %4.0f iterations of while loop, we find\n',count)
fprintf('  unitroundoff = %14.8g \n',ubig)
echo on
%
% matlab provides this value through the variable "eps"
help eps
% and we can see this value without computing our own
% version in the while loop above by simply printing it
% out by given the variables name on the MATLAB command line
format short e
eps

>> diary off