Program cards having projections extending from one surface are formed so that they can be interconnected in the longitudinal and transverse directions to provide a continuous member of increased length or width. Corresponding edges of the cards are reduced in thickness and are provided with projections on one and perforations in the other so that they can be joined together with the overall thickness of the joined edges being equal to the normal thickness of the card. To increase the flexibility of the card, the surface which does not contain the projections is provided with recesses which extend transversely of the longitudinal direction of the card. In addition, a rack is formed along one edge of the cards to assist in moving the cards through the control apparatus. A clamping strip can be used to assist in joining cards together.
