I think you can use anything you please. I've found it useful to identify formula fields by prefixes, L_logic, C_Calc, D_display. And in running totals, G_value for group totals and T_value for overall, maybe G1_tot and G2_tot if there is more than one group.
Parameters could be P_whatever, but since the various types have their own symbol, @ or # or ?, is it needed?
Madawc Williams
East Anglia
Great Britain