Coding/decoding process and device, for instance for disk drives

The signals that are to be transferred, i.e., written (161) and/or read (17), with respect to the sectors of a storage medium, such as a hard disk, are encoded by using at least two error-correction codes (12, 14). Two error-correction codes (ECCs) are used of the Reed Solomon type, namely an inner code (12) and an outer code (14). At the encoded level, the user data are organized in a matrix structure comprising a first set of data sectors (for example, sixteen data sectors) and are encoded, respectively, by means of the inner code (12) in the horizontal direction of the matrix and by means of the outer code (14) in the vertical direction of the matrix. The redundancy of the outer code (14) is organized in a second set of redundancy sectors, which comprises, for example, two redundancy sectors, written and/or read with respect to said storage medium as the sectors of said first set.