function square(a0,b0,length)
%square.m Demonstrating the loop and
% graphics interaction
%

a=a0;
b=b0;
len=length; % length
x(1)=a;
x(2)=x(1)+len;
x(3)=x(2);
x(4)=x(3)-len;
%--------------------
y(1)=b;
y(2)=y(1);
y(3)=y(2)+len;
y(4)=y(3);
%
line([x(1) x(2)],[y(1) y(2)]);
text(x(1),y(1),num2str(1));
%
line([x(2) x(3)],[y(2) y(3)]);
text(x(2),y(2),num2str(2));
%
line([x(3) x(4)],[y(3) y(4)]);
text(x(3),y(3),num2str(3));
%
line([x(4) x(1)],[y(4) y(1)]);
text(x(4),y(4),num2str(4));