Compared to positional numeral systems, the unary system is inconvenient and is not used in practice. It would be cumbersome, for instance, to calculate 500 + 700 in the unary system. It occurs in some problem descriptions in theoretical computer science (e.g. some P-Complete problems), where it is used to "artificially" decrease the run-time or space requirements of a problem. For instance, the problem of integer factorization is suspected to require more than polynomial run-time if the input is given in binary, but it only needs linear runtime if the input is presented in unary.
wikipedia.org dumped 2003-03-17 with terodump