Classes for manupulating rows and changes, and all the other classes and functions described in this chapter, are declared in ringing/row.h.
For ease of notation, we use the idea that a row is an individual permutation of bells (such as 13572468), and a change is a means of getting from one row to another, by swapping pairs of bells; the most convenient way to write a change is a place notation (for example X or 1258).