HP 12C "Solve LOG from TVM funtions"

[bshoring]

Joe's right.

However, because the first two HP Financial calculators do not have the LN function, HP did provide a way to compute LOG & LN using the financial keys on the HP-80, and LOG on the HP-70.

Since the HP-80 does all its computations in the stack, if you follow HP's instructions to get a LOG, the LN is automatically left in the Y register.

HP-70, like all that follow, uses dedicated financial registers, so the Y reg will not contain LN, but there still is a way to compete LN on it if one puts the right input into the Interest (i) register.