Matrix Matlab

Can someone help me annotate the 4 required field, im totally lost, I HATE MY SCH!

Appendix A: Code for Assignment Question 3

function x = Gauss(A, b)
% Solve linear system Ax = b
% using Gaussian elimination without pivoting
% A is an n by n matrix
% b is an n by k matrix (k copies of n-vectors)
% x is an n by k matrix (k copies of solution vectors)

[n, k] = size(b); % Annotate this
x = b; % Annotate this
for i = 1:n-1
m = -A(i+1:n,i)/A(i,i); % Annotate this
A(i+1:n,:) = A(i+1:n,:) + m*A(i,:); %Annotate this
b(i+1:n,:) = b(i+1:n,:) + m*b(i,:);
end;

% Use back substitution to find unknowns
x(n,:) = b(n,:)/A(n,n);
for i = n-1:-1:1
x(i,:) = (b(i,:) - A(i,i+1:n)*x(i+1:n,:))/A(i,i);
end