mexFunction is not a routine you call. Rather, mexFunction is the name of the gateway function in C (subroutine in Fortran) which every MEX-file requires. When you invoke a MEX-function, MATLAB® software finds and loads the corresponding MEX-file of the same name. MATLAB then searches for a symbol named mexFunction within the MEX-file. If it finds one, it calls the MEX-function using the address of the mexFunction symbol. MATLAB displays an error message if it cannot find a routine named mexFunction inside the MEX-file.