HP21 calculation accuracy

[Ian Hoogeboom]

Hello,

I bought an non-working HP21 at a flee market, but after cleaning it's interior it works fine... I think. It's not so accurate (anymore), 2yx10 results in 1023.999999 instead of 1024 (all yx functions are not correct). Functions like tan 89.9995 result in 114585.0362 instead of 114591.559. Is this normal as this machine is more than 20 years old or is there something broken in the calculation part of it?

Thank you in advance,

Ian Hoogeboom.

[Mike Sebastian]

Early HPs, including your HP-21 only computed results to ten digits, with no guard digits. Modern HPs and many other modern calculators compute results to at least 12 digits, then round to ten digits. Your calculator is working correctly. The results you are observing are consistent with calculators of that era.

[Ian Hoogeboom]

Mike,

Thank you for your reaction!

Kind regards,

Ian Hoogeboom.