Abstract: A computer system for electronically storing and retrieving data files which have been linked together to form a hierarchal information tree having a plurality of mutually exclusive branches corresponding to the information represented by the data files and which has been classified at various levels in the hierarchal structure of the tree. The computer system has a central processing unit that is electronically coupled to input/output apparatus which includes a keyboard, a CRT screen, a printer and, if desired, an analog/digital input device. An electronic storage means is electronically coupled to the CPU. The storage means contains a system control program together with the data base of files linked together to form the expandable hierarchal tree. A separate portion of the storage means, or a second storage device also contains a system control program together with addressable files which may be used to store information which is retrieved as the CPU searches the data base.