1. A display and edit device for a program containing function blocks, said function blocks serving to use a language element referred to as function block definitions to establish input and output parameters, internal variables and operations algorisms of the function block and to create copies referred to as function block instances by instantiating said function block definitions when said function block is incorporated in a user program, said device comprising: a program memory storing said program; a block definition analyzer for accessing said program stored in said program memory and analyzing structure relationship of function block definitions contained in said program; a block instance analyzer for accessing said program stored in said program memory and analyzing structure relationship of function block instances contained in said program; a structure display device for causing to simultaneously display structure relationship of the analyzed structure relationship of said function block definition and structure relationship of the analyzed structure relationship of said function block instance; an instance display device for causing to display a selected function block definition or a selected function block instance together with said structure relationship of the analyzed structure relationship of said function block definition and said structure relationship of the analyzed structure relationship of said function block instance; and a display judging device for causing said structure display device to display with an emphasis the structure relationship of said selected function block definition or selected function block instance or a corresponding portion of the structure relationship of the function block instance; wherein, when a function block included in said selected function block instance displayed by said instance display device is selected, said display judging device causes said structure display device to display with an emphasis said function block in the structure relationship of said selected function block instance; and wherein, when a function block included in said selected function block definition displayed by said instance display device is selected, said display judging device causes said structure display device to display with an emphasis said function block in the structure relationship of said selected function block definition.