A method of effecting a matrix transpose operation in a computer is described. The method uses a computer instruction which restructures a data string by retaining first and last sub-strings of the data string in unchanged positions and interchanges the position of at least two intermediate sub-strings. The data string is formed from sub-strings each representing one or more data value in a matrix. The computer instruction can be effected in a single register store having a predetermined bit capacity addressable by a single address, or in a pair of such register stores. The data restructuring instructions include "flip", "zip" and "unzip" instructions.