yes its a user defined function as u can see in the image "zconv2" is a c mex file.where it does'nt link with the program which is in the same folder of the above function.As per the PDF information given by u sir,i just checked the c compilers in the MATLAB version am having its nil over there.Now the different thing is that the when i ran the same prgm in another system,it works and i checked its c compiler and its there.
i got the answer myself,i just googled and found that my program needs the C compiler in order to link the main code and the secondary function code. i just installed microsoft visual studio 10 and just setup the mex setup.
it was working in a click.......thanks all for giving answers