MATLAB Code for simualting the spreading using Walsh Codes

[Anne]

A = [-1 -1 1 1]; %Spread waveform representation of user A's signal
B = [-1 1 -1 1]; %Spread waveform representation of user B's signal
C = [1 1 -1 -1]; %Spread waveform representation of user C's signal

% Generating the code and its timing sequence:

% to generate a 4 x 4 Hadamard matrix (which is the matrix of 1's and -1's
% and the columns are orthogonal):
N = 4;
H = hadamard(N);
% Picking full second row of Hadamard matrix:
cA = H(2,:);
% Picking full third row of Hadamard matrix:
cB = H(3,:);
% Picking full fourth row of Hadamard matrix:
cC = H(4,:);

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

% Initializing empty matrices:
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
codeA
% 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
Tx_data

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;

note:
please help me in understanding each statement of this code.