When the initial configuration is produced it is written on magnetic tape in the obvious manner—one row of mesh points per tape block.
(On the Univac, just one mesh point per block.)
Instead of rewinding the tape at the end, the tape is read backwards and the mesh calculation for the 2nd time step is computed backwards.
This is written onto another tape which itself will be read backwards during the calculation of the 3rd time step.
This strategy avoids waiting for tape rewind.
This to-and-fro pattern has some advantages in the case of modern memory caches.


<hr>See <a href=../../Software/TRTape.html>too</a>.