Calculation of determinant on HP-15C

[Thomas Okken]

Only if you mean "numeric" as opposed to "symbolic." The algorithms are not approximations in the sense of numerical iterative methods; in infinite precision, they would be exact. But with finite precision, you will get results that aren't exact even if the algorithm is exact in principle. This is essentially the same phenomenon as what causes 1 ENTER 3 / 3 * 1 - to return a nonzero result.