item of attribute node ea13 and a pointer to type node tt14 is written into the fourth item of attribute node ea14 if the answer is negative in decision block 15 of subroutine 16 has been executed control proceeds to subroutine 17 which directs the type node generating means 3 to write a value indicative of the type of each node into the first item of that node and directs the internode linking means 5 to detect a pointer linking each type node to a higher ranking attribute node if there is one and writes the pointer into the second item of type nodes if there is no subelement a null pointer is written into the second item of type nodes as shown in fig7 for example 34 integer 34 34 ia5string 34 and 34 sequence 34 are written into the first item of the type nodes tt11 tt12 and tt14 respectively and a null pointer is written into the second item of type nodes tt11 and tt12 and a pointer to attribute node ea13 is written into the second item of type node tt14 in this way attribute node and type nodes are linked in tree form in operations block 14 the c language declaration sentence generating means 6 traces the links between the various nodes and generates character strings written in the c programming language as shown in fig8 which are available as an output of the data structuring apparatus 10 to be processed in a c language program as a result protocols structured in accordance with.