page numbers were from one to nine digits in length, i.e., in the range 0 to 999999999 created in a tree like structure, whereby lower level pages could only exist if the higher numbered "parent" pages had already been created. thus creating page 7471 required pages 747, 74 and 7 to exist, but generally the three digit node 747 would have been created in order to register the relevant main ip account. single and double digit pages were special pages reserved by prestel for general system information purposes, as were the 1nn-199nn sets of three digit nodes e.g. page 1a was the standard prestel main index. pages starting with a 9 were for system management functions, and were limited to three digits in length. e.g., page 92 showed details of the users prestel bill, and page 910 gave ips access to online editing facilities.