There is an optional arguments for the functions load, save, loadmesh, savemesh. This is the 2nd or 3rd argument of these functions. Here are the prototypes:
save(<filename>, <function name> [,<variable counter: integer or converted to integer>]) load(<filename>, <function name> [,<variable counter: integer or converted to integer>]) savemesh(<filename>[,<variable counter: integer or converted to integer>]) loadmesh(<filename>[,<variable counter: integer or converted to integer>])
As an example see nsstepad.pde which use this feature to save the
mesh and the solution at each adaptation of the mesh. This special feature
allows you to save or load a generic filename with a counter, the final
filename is built like this '<generic filename>-<counter>'.