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HP Forum Archive 17

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HP-70 INT key function
Message #1 Posted by Dave Smith on 23 May 2007, 5:35 a.m.

Could anyone please help me with the way in which the INT key is used on an HP-70. I have an HP-70 in perfect condition (as far as I know) that I plan to sell, but I don't know how to check fully the INT key function - all the others are OK.

On most (HP) calculators INT means INTEGER but on this one I guess it means INTEREST of some kind. I just don't know which combination of the n, i, PMT, PV & FV entries have to be entered to use this and what calculation is then performed. Most uses of this give me an flashing display illegal operation warning, but on the odd occasion I have got a result but can't remember how I got it!

Thanks for any help received.

      
Re: HP-70 INT key function
Message #2 Posted by Gene on 23 May 2007, 7:31 a.m.,
in response to message #1 by Dave Smith

Check the 12c manual, available online free, for it's INT function. Should help you here.

            
Re: HP-70 INT key function
Message #3 Posted by Eric Smith on 23 May 2007, 4:12 p.m.,
in response to message #2 by Gene

Note that the HP-80, HP-81, HP-70, HP-22, and HP-27 do not have the same five-variable TVM solver as later models. They only support certain combinations of four TVM variables, and do not use the sign convention for the direction of cash flow. Thus examples for the 12C won't work on the HP-70 without changes.

The HP-80 and HP-81 are even more primitive; they don't actually have registers to store the financial variables, but rather use the stack. If you try to calculate the values you're going to use, you may push some of your values off the four-level stack, and get the wrong answer from the TVM calculation.

                  
Re: HP-70 INT key function
Message #4 Posted by Dave Smith on 23 May 2007, 4:16 p.m.,
in response to message #3 by Eric Smith

Thanks Eric, and to Gene, too, for his earlier reply. I checked out the 12c manual and realised the convention. The INT key works as it should do. I am most grateful for this prompt help.


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