Can anyone explain me this matlab code in detail??

iphat_re

This is a matlab code which gives u a Symbol error probability curve for 64-QAM modulation .
Now I want someone to explain me this code in detail right from the beginning . How does it work ?? I would really appreciate that .

Here is the Code:
--------------------------------------------------------------------------
N = 7*10^5; %% number of symbols
M = 64; %% number of constellation points

k = sqrt(1/((2/3)*(M-1))); %% normalizing factor

m = [1:sqrt(M)/2]; %% alphabets
alphaMqam = [-(2*m-1) 2*m-1];

Es_N0_dB = [0:30]; %% multiple Es/N0 values

ipHat = zeros(1,N); %% init

for ii = 1:length(Es_N0_dB)

ip = randsrc(1,N,alphaMqam) + j*randsrc(1,N,alphaMqam);
s = k*ip; %% normalization of energy to 1
n = 1/sqrt(2)*[randn(1,N) + j*randn(1,N)]; % white guassian noise, 0dB variance

y = s + 10^(-Es_N0_dB(ii)/20)*n; %% additive white gaussian noise

%%demodulation
y_re = real/k; % real part
y_im = imag/k; % imaginary part

%% rounding to the nearest alphabet
%% 0 to 2 --> 1
% 2 to 4 --> 3
% 4 to 6 --> 5 etc
ipHat_re = 2*floor(y_re/2)+1;
ipHat_re(find(ipHat_re>max(alphaMqam))) = max(alphaMqam);
ipHat_re(find(ipHat_re<min(alphaMqam))) = min(alphaMqam);

%% rounding to the nearest alphabet
%% 0 to 2 --> 1
%% 2 to 4 --> 3
%% 4 to 6 --> 5 etc
ipHat_im = 2*floor(y_im/2)+1;
ipHat_im(find(ipHat_im>max(alphaMqam))) = max(alphaMqam);
ipHat_im(find(ipHat_im<min(alphaMqam))) = min(alphaMqam);

ipHat = ipHat_re + j*ipHat_im;
nErr(ii) = size(find([ip- ipHat]),2); %% counting the number of errors

end

simSer = nErr/N;
theorySer = 2*(1-1/sqrt(M))*erfc(k*sqrt((10.^(Es_N0_dB/10)))) ...
- (1-2/sqrt(M) + 1/M)*(erfc(k*sqrt((10.^(Es_N0_dB/10))))).^2;
close all
figure
semilogy(Es_N0_dB,theorySer,'bs-','LineWidth',2);
hold on
semilogy(Es_N0_dB,simSer,'m*-','Linewidth',1);
axis([0 30 10^-5 1])
grid on
legend('theory', 'simulation');
xlabel('Es/No, dB')
ylabel('Symbol Error Rate')
title('Symbol error probability curve for 64-QAM modulation')
--------------------------------------------------------------------------------