Abstract: A system of and method for writing and reading data on magnetic tape records having the capability of searching for certain data files in which selected messages are written is disclosed. The files are written successively on the tape with a name block which identifies or describes the files and data block which constitute the files written alternately to constitute the file format. The file names are written at much less than the normal data density. When reading the files, search operations are carried on at high tape speed; the ratio of the high tape speed to normal tape reading speed being the same ratio as the ratio of the normal density of recording of the data block to the lower density of recording of the file names in terms of bits per linear inch. The bit rate produced while reading the file names at high speed is then exactly equal to the bit rate generated while reading data blocks at low speed.