Matlab: process a sequence of files

1. My regular solution
for i=1:20
 temppp = ['C:\Data\SuperImage\images\just_zoom_',num2str(i),'.bmp'];
 input_img = imread(temppp);
end

2. another one
for i=1:20
temppp =sprintf('C:/Data/SuperImage/images/just_zoom_%d.bmp',i); %back slash
 input_img = imread(temppp);
end

3. process all the files in a directory

d=dir('*.bmp');
for k=1:length(d)
  fname=d(k).name;
  input_img = imread(fname);
end