Undefined function or method 'imsharpen' for input arguments of type 'uint8'.

if true
  % code
d1=imread('j.jpg');

b = imsharpen(d1);

subplot(2,2,4); imshow(b); title('Sharpened Image'); end

Answer 1

[Image Analyst]

Type ver at the command prompt. Do you see the Image Processing Toolbox:

MATLAB                               Version 8.3        (R2014a)
Image Acquisition Toolbox            Version 4.7        (R2014a)
Image Processing Toolbox             Version 9.0        (R2014a)

imsharpen is in that toolbox. If you don't have that toolbox, that would explain your error.