Data processor having multilevel address translation tables

An information processing system including a group of translation tables in a multilevel structure for achieving address translation from a virtual address into a real address, a control register for keeping a starting point address data of a translation table located at a highest level among the address translation tables and a level data indicating a level (n) of the translation table at the highest level among the group of translation tables, and a unit for sequentially accessing the address translation tables at levels lower than the level (n) indicated by the level data in the control register based on the starting point address data and a virtual address to be translated, thereby translating the virtual address into a real address.