A Simple Description of an Error-Correcting Code for High-Density Magnetic Tape

The latest IBM tape units use f-in., nine-track tape with the very high density of 6250 bits per in. This is made possible, in part, by the use of an efficient error-correcting code, which can correct errors in one or two tracks. The code was described by Patel and Hong 1 (see also Ref. 2), and is a straightforward extension of earlier IBM codes (see Refs. 3 and 4). The purpose of this paper is to give a simple description of the code and its many nice features, without using Galois fields.