Let us consider a case in which four preceding lists (A)
are present before the data of urea (BV) are treated (Figure
2, left). Figure 2 (right) illustrates how the atom code list
in Figure 1 (B) is put into the preceding tree files (A). First
the root atom code a of (B) is compared with the one in the
root tree file (A). There is already the atom code a in it.
Hence it is not added in the root tree file. The second sphere
atom code b of (B) is found not to match the first code a in
the second tree but to match the second code b. The b in
the second tree file has an address arrow only to b in the
third tree file at the stage of A. After the registration of
(B), the new atom codes “c,c” are added at the end of the
third tree file, and a downward arrow (address) is drawn to
show the parent-child relationship. The whole conversion
job for the 80 000 structure data totally makes 105 tree files,
which include spheres up to the 105th sphere at most.