simualting the spreading using Walsh Codes

A = [-1 -1 1 1]; B = [-1 1 -1 1]; C = [1 1 -1 -1];

% Generating the code and its timing sequence:

N = 4; H = hadamard(N);

cA = H(2,:); cB = H(3,:); cC = H(4,:);

% Number of samples per chip: Tc_samp = ones(1,4);

codeA = []; codeB = []; codeC = [];

for k = 1 : length(cA)

    codeA = [codeA cA(k)*Tc_samp];
    codeB = [codeB cB(k)*Tc_samp];
    codeC = [codeC cC(k)*Tc_samp];

end

% Generation of Tx Data:

Tx_data = [];

for k = 1 : length(A)

    uA = A(k)*codeA;
    uB = B(k)*codeB;
    uC = C(k)*codeC;

    Tx_data = [Tx_data uA+uB+uC];
end

NN = length(Tx_data)

uAb = []; uBb = []; uCb = [];

for k = 1 : NN / 16

    index = (k - 1)*NN/4 + 1 : k*NN/4;
    uAb = [uAb sum(Tx_data(index).*codeA)];
    uBb = [uBb sum(Tx_data(index).*codeB)];
    uCb = [uCb sum(Tx_data(index).*codeC)];

end uAb % Error:

 res1 = A-uAb/16;
 res2 = B-uBb/16;
 res3 = C-uCb/16;

i am unable to understand this code , help me in understanding every statement of this code.