(a) In all cases, including criminal, quasi-criminal and civil, when a person is imprisoned, incarcerated, confined or committed to the custody of a sheriff, warden, Department of Corrections or other executive officer by virtue of a judgment or order which is signed by a judge, a copy of such judgment or order shall, in each case, constitute the mittimus, and no separate mittimus need be issued.
     (b) Where no written judgment or order was signed by a judge, the practice heretofore prevailing in such cases in the courts of this State shall be followed.