19. The apparatus according to claim 17 , wherein the processing unit is further configured to select cells from the free cells as selected cells, wherein the selected cells are cells which are selected from the free cells readable to provide a specified message or a specified part of a message.
19. The apparatus according to claim 17 , wherein the processing unit is further configured to select cells from the free cells as selected cells, wherein the selected cells are cells which are selected from the free cells readable to provide a specified message or a specified part of a message. 20. The apparatus according to claim 19 , wherein the processing unit is configured to assign decode input values to the selected cells such that the encoded message includes a URL of a network resource.