# special functions, initializations

A = zeros(5);  # create 5x5 matrix filled with zeros
B = ones(7);   # create 7x7 matrix filled with ones
I = eye(10);   # create 10x10 matrix filled with ones on diagonal and zeros elsewhere

E1 = [ [ 1, 2, 3],
       [ 4, 5, 6],
       [ 7, 8, 9] ];


A[1,3] = 0 ;
