sentences:  Because instruction execution is still restricted to the program address space, these processors are very unlike von Neumann machines.Having separate address spaces creates certain difficulties in programming with high-level languages that do not directly support the notion that tables of read-only data might be in a different address space from normal writable data (and thus need to be read using different instructions).The C programming language can support multiple address spaces either through non-standard extensions or through the now standardized extensions to support embedded processors.