% Comments (non-executed instuctions) always begin with
% the PERCENT SYMBOL.

% This is a function statement.
% When we type:
% locker(10)
% in the Command Window, the script
% locker.m  will be executed with 10 lockers!
function y = locker(n)
% The variable a is an n-by-1 column vector of zeros.
% 0 = closed and 1 = open!
a = zeros(n,1);
% This identifies which student is playing with the
% lockers.  We begin with student #1 and then eventually
% move up to student #n.
for i = 1:n
    % This loop is nested inside the first one.
    % This starts with j = i, and then
    % STEPS by i units.
    % For example:
    %   for j = 3:3:20
    % will produce j = 3, then j = 6, then j = 9,
    % until we reach 20.  Notice that j = 18 is the
    % last number generated.
    for j = i:i:n
        % If the jth locker is closed, then open it.
        % Else, if the jth locker is open, then close it.
        % Note that the logical test for "equals" is "==".
        if a(j,1)==0;
            a(j,1)=1;
        else
            a(j,1)=0;
        % Every "if" statement needs an "end".
        end
    % Every "for" loop needs an "end".    
    end
end
for i = 1:n
    % This is the print statement.
    % We will print the locker number i, and its status.
    fprintf(' %5.0f  %2.0f\n',i,a(i,1));
end