What variables should i choose inside the loop?

Suppose I have NN number of images named img1 to imgNN...what variables should I choose to display all the images inside the loop..

NN = 40;
for ii = 1:NN
  figure;
imshow(img(NN));
axis on;
end

I tried this but its not working...I am facing trouble choosing the variable..any help is appreciated

Answer 1

[Walter Roberson]

NN = 40;
for ii = 1:NN
  figure;
  thisimgname = sprintf('img%d.jpg', ii);
  img = imread(thisimgname);
  imshow(img);
  axis on;
end

[peyush]

thanks