%file name: hamma.m
%Written by Dr. James S. Kang, Cal Poly Pomona.
%Calculate the codeword for the given data u when Hamming code is used.
%u = input data such as [0 1 0 1].
%v = codeword = [u c], where c is the checking part.
%To run the program, try
% >>hamma([1 1 0 1])  <Enter>
function[H,G,v] = hamma(u)
k=size(u,2); %k = length of u.
m=ceil(log(k)/log(2));
if 2^m-1-m < k m=m+1; end
n=k+m;
Im=eye(m);
Q=zeros(m,k);
nc = 0; %nc = number of columns in Q matrix.
count=0; 
d=zeros(m)';
while nc < k
   count=count+1;
   b=dec2bin(count);
   if sum(b)>1
      nc=nc+1;
      s=size(b,1);
      if s<m
	 for j=1:s d(m-s+j)=b(j); end
	 for j=1:m b(j)=d(j); end
      end
      Q(:,nc)=b;
   end
end
H=[Q Im];
Ik=eye(k);
G=[Ik Q'];
disp('Generator Matrix G = ');
disp(G);
v=rem(u*G,2);
disp('codeword v = ');
disp(v);
disp('Parity Check Matrix H = ');
disp(H);