1. A microprocessor comprising: a processing unit; a memory connected to said processing unit and comprising an addressable memory space for a lower memory area and an extended memory area; means for connecting to and accessing said addressable memory space; means for executing an instruction set for accessing said addressable memory space, the instruction set comprising a first instruction group for accessing said lower memory area, and a second instruction group distinct from the first instruction group for gathering instructions in the instruction set for accessing said extended memory area; and means for preventing access to said extended memory area when executing the first instruction group.