MATLAB: Were to introduce hold on command

circle

I  have a image in which i have to draw a circle over it,i have to draw circles in many places in the image ,please tell how to procees,i saw a code in matlab central it draws only one circle ,but how to draw many circles on a image manually ,i have to click on image and have to draw circle
http://www.mathworks.com/matlabcentral/fileexchange/23121-circle-on-image
i edited from above link but the thing is that i have to draw many circle on one image ,please tell where i have to write hold on command  
code
where k is my image 
function [] = circle_saptha(k)
ok = 0;
while ok~=1
    % figure;

      imshow(k);
      pt = ginput(2)
      x1 = pt(1,1);
      y1 = pt(1,2);
      x2 = pt(2,1);
      y2 = pt(2,2);
      xpt = [x1 x2];
      ypt = [y1 y2];
      %line(x,y); % Enablw this for draw rectangle on circle
      r = sqrt((x2-x1)^2 + (y2-y1)^2)
      pp=rsmak('circle',r,[x1 y1]);
      % figure;
      % imshow(k)
      fnplt(pp);
      line(xpt,ypt);
      xtl = x1-r;
      xtr = x1+r;
      xbl = x1-r;
      xbr = x1+r;
      ytl = y1+r;
      ytr = y1+r;
      ybl = y1-r;
      ybr = y1-r;
      x = [xtl xtr xbr xbl xtl];
      y = [ytl ytr ybr ybl ytl];
      %line(x,y);
      for i=1:size(k,1)
          for j=1:size(k,2)
              x2 = j;
              y2 = i;
              val = floor(sqrt((x2-x1)^2 + (y2-y1)^2));
              if(val == floor(r))
                  nim(i,j,1) = 255;
                  nim(i,j,2) = 0;
                  nim(i,j,3) = 0;
              else
                  nim(i,j,1) = k(i,j,1);
                  nim(i,j,2) = k(i,j,2);
                  nim(i,j,3) = k(i,j,3);
              end
          end
      end
      imshow(nim);
      ok = (menu('Do u want to draw another circle?','No','Yes')==1)
      imshow(nim);
  end
  end

Best Answer

You keep overwriting "nim" with the same original "k". You can fix it easily:
Step 1. Change these lines:
ok = 0;
while ok~=1
    % figure;

      imshow(k);
to this:
ok = 0;
nim = k;
while ok~=1
    % figure;
      imshow(nim);
Step 2. Delete these three lines:
   nim(i,j,1) = k(i,j,1);
   nim(i,j,2) = k(i,j,2);
   nim(i,j,3) = k(i,j,3);
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