Use of Tree Structures for Processing Files In data processing problems, files are frequently used which must both be searched and altered. Binary search techniques are efficient for searching large files, but the associated file organization is not readily adapted to the file alterations. Conversely, a chained file allocation permits efficient alteration but cannot be searched efficiently. A file organized into a tree-like structure is discussed, and it is shown that such a file may both be searched and altered with times proportional to slog(s)N, where N is the number of file items and s is a parameter of the tree. It is also shown that optimizing the value of s leads to a search time which is only 25 per cent slower than the binary search. The tree organization employs two data chains and may be considered to be a compromise between the organizations for the binary search and the chained file. The relation of the tree organization to multidimensional indexing and to the trie structure is also discussed. CACM May, 1963 Sussenguth Jr., E. H. CA630518 JB March 14, 1978 10:49 AM 435 4 849 2846 4 849 849 4 849 849 4 849 944 4 849 155 5 849 1050 5 849 1935 5 849 1936 5 849 2017 5 849 2032 5 849 2257 5 849 2360 5 849 2451 5 849 2452 5 849 615 5 849 849 5 849 849 5 849 849 5 849 849 6 849 849 6 849 849 6 849 849 6 849 849 6 849 849 6 849 849 6 849 849 6 849 849 6 849 850 6 849 851 6 849 852 6 849 853 6 849 854 6 849 855 6 849 856 6 849 857 6 849 858 6 849 859 6 849 860 6 849 861 6 849 862 6 849 863 6 849 864 6 849 865 6 849 866 6 849 106 6 849 944 6 849 1115 6 849 1785 6 849 209 6 849 1831 6 849 1831 6 849 1935 6 849 1936 6 849 1936 6 849 1936 6 849 1936 6 849 1976 6 849 367 6 849 2198 6 849 2360 6 849 627 6 849