1. In an interpretive-type electronic digital data processing system for performing data processing operations, the combination comprising: a multi-level hierarchy of processors for performing data processing operations, said hierarchy of processors being designatable in descending hierarchical order as S, M, N and P processors and being constructed and arranged such that said M-processor serves as a control section for said S-processor, said N-processor serves as a control section for said M-processor and said P-processor serves as a control section for said N-processor; said S-processor including an S memory for storing S instructions corresponding to one or more high level languages; said M-processor including an M memory for storing M instructions; said N-processor including an N memory for storing N instructions; means for applying S instructions to said N-processor; said N-processor including means responsive to an applied S instruction for fetching a selected one or more M instructions from said M memory and for applying the fetched one or more M instructions to said P-processor; said P-processor including means responsive to a fetched M instruction for fetching a selected one or more N instructions from said N memory and in response thereto producing an N-level command which is applied to said N-processor; said N-processor being responsive to an applied N-level command for processing a fetched M instruction to produce an M-level command which is applied to said M-processor; said M-processor being responsive to said M-level command for processing applied data in accordance therewith.