1. A data processor comprising: a processor with a predetermined instruction group as its native codes; a hardware translator converting a code which is non-native to said processor into one or more native codes of said processor; and a memory storing a program constituted by a native code operating on said processor, said program stored in said memory including a software translator program operating on said processor to convert a code that is non-native to said processor into one or more native codes of said processor and storing the converted native code in said memory, a software interpreter program operating on said processor to sequentially interpret a code that is non-native to said processor and executing said interpreted code using a native code of said processor, and a select program to select any of execution of a native code output by said hardware translator, execution of a native code output by said software translator and stored in said memory, and sequentially interpreting and executing non-native code by execution of said software interpreter according to a predetermined criterion to operate said processor.