[x,map]=imread('C:\MATLAB6p5\toolbox\images\imdemos\circlesm.tif');
[x1,map]=imread('C:\MATLAB6p5\toolbox\images\imdemos\circles.tif');
figure;
imshow(x,map); title('original image');
c=not(x);
figure;
imshow(c,map);title('not operation');
disp('press a key');
pause;
clear c; 
x2=x(1:256,1:256);
figure; imshow(x2,map); title('original image');
c=or(x2,x1);
figure;
imshow(c,map); title('or operation');
disp('press a key');
pause;
%clear c; clf
%c=imsubtract(x1,x2);
%figure;
%imshow(c,map), title('sub operation');
%disp('press a key');
%pause;