Patent ID: 8712557

Claim:
A control-system maintenance tool, comprising a program editor which: reads element data for representing circuit elements and operators and attribute values of said element data from data storages, said circuit elements and said operators being components of sequential programs which constitute functions of said control system; creates a program-edit screen for said control system based on said read element data; edits said element data on said created program-edit screen in accordance with an editing input from an input device; and comprises a judgment function of judging whether said element data for representing said circuit elements and said operators is protected-function data or non-protected-function data, said control-system maintenance tool displaying assembly sets of a plurality of said circuit elements, operators whose inputs are outputs from these circuit elements, and circuit elements whose inputs are outputs from these operators on said program-edit screen; and displaying assembly sets of programs constituted by circuit elements and operators to which accesses are authenticated for implementing a predetermined function on said program-edit screen in a display mode different from display modes of other assembly sets; wherein said assembly sets of said programs constituted by said circuit elements and said operators to which said accesses are authenticated are displayed on one and the same screen of a display device in said display mode different from said display modes of said other assembly sets; once an element data is edited, other element data which would affect circuit elements to which accesses are authenticated are searched for and all the affecting circuits are displayed as protected objects.