1. An information retrieval system for retrieving data from a database, said system comprising: input means for admitting textual input information for designating retrieval of the data from the database, said textual input information being sufficient to at least partially correspond to said data; conversion means for categorizing said textual input information and for converting the categorized information into input data in bit strings; and a neural network, including at least an input layer for admitting said input data and an output layer for outputting output data indicating those data in said database which correspond to said textual input information, for changing, during a learning process, the weight of connection between said input layer and said output layer when said input data are admitted into said input layer.