# Calculator model with mod function?

I'm wondering does anyone know of a scientific calculator with a mod function?

In C# this is shown as follows (just in case there are any other mods that a mathematical non-savant such as myself wouldn't be aware of)

5 % 4 = 1

I've looked through the most common ones on the web but the function is either not in the list or not present.

I have a little bit of a bias towards Casio calculators as that's what I'm familiar with but will accept any suggestions that can be currently purchased.

Derek

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Do you want exponentiation modulo a number as well? As you tag it cryptography? This is a bit harder than just the modulo operation, as $a^b \pmod{n}$ is not computed by finding $a^b$ first, but by a process that has intermediate reductions, to keep numbers small. Of course, python (as a command line calculator) and similar programs (Pari, etc.) will do this on a computer. – Henno Brandsma Mar 16 '11 at 15:21
If you use Windows 7 I desire the same functionality as the mod function that calculator offers. I'm afraid I don't know enough to comment on your observation :-( – noonand Mar 16 '11 at 16:24
Why do you want a calculator model? – Mariano Suárez-Alvarez Mar 16 '11 at 17:40
Doing a Masters and I need it for exams... – noonand Mar 17 '11 at 22:04
My calculator has a % key ... but it doesn't do mod, it does percentage. – GEdgar Jul 13 at 15:56

Virtually every graphing calculator made in the recent past has a mod function. Many scientific calculators do as well, though the documentation is often lacking.

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@noonand: Casio classifies the fx-85GT as a "Standard Scientific Calculator" and shows no graphing features in the manual. – Isaac Mar 18 '11 at 14:55
Apparently the Casio FX 991ES Plus does this I have an email from the Casio distributor in Ireland to this effect. I'm a little bit dubious as the manual makes no reference to a modulo function but I'm also mindful of @Isaac's comment about documentation above. – noonand Mar 28 '11 at 15:47
@noonand: My concern with the FX 991 ES Plus is that looking at images of it, I can't see where the modulo function would be—I don't see a key labeled for it, nor would it make sense to me for it to be in any of the menus based on the menu names. – Isaac Mar 28 '11 at 17:50
@noonand: The TI-34 MultiView has a "remainder" function. – Isaac Mar 28 '11 at 17:58
Just not true, most Casio's don't have a modulo function whatsoever. Of course you can program the functionality in, though. – Benjamin R Oct 25 '15 at 0:59

HP : buy a hewlett packard calculator. the model HP-35S contains hundreds of functions. there is a description here ; http://www.shopping.hp.com/product/calculator/Scientific/1/storefronts/F2215AA%2523ABA;HHOJSID=FW7TNQVJMqHh075qvYbPbRvjvx2K1ybHFyYXGDY9Vr8kpqFlknwg!492383249

The 32Sii used to have a button just for that, on the other hand the HP35s is programmable and you can most probably do it easily.

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Thanks very much - appreciate your time! – noonand Mar 16 '11 at 11:51
While HPs are great and I wouldn't trade my multitude of HPs for any other calculators past or present, the good ones (like the 32s/33s/35s and the 48g/49g/50g series) require learning RPN/postfix notation (though RPN is one of my primary reasons for liking the HPs so much). – Isaac Mar 18 '11 at 2:58
The 49G and 50G added an "algebraic" mode which uses the usual infix notation. – Nate Eldredge Mar 18 '11 at 3:02
@Nate: Ah, right. Most people are probably better off with a TI-84 or TI-Nspire than an HP 49G/50G, though. – Isaac Mar 18 '11 at 14:59
Cannot mark as useful as don't have enough rep; will circle back and do so ASAP ;-) – noonand Mar 28 '11 at 15:49

GeoGebra has a Mod[a,b] command eg

http://web.geogebra.org/?command=Mod[5,4]

If you want to define it to use as a function you can do

mod(x, y) = y (x / y - floor(x / y))

and then use that, eg

http://web.geogebra.org/?command=mod(x,y)=y(x/y-floor(x/y));mod(5,4)

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You can calculate mod on any calculator with this algorithm:

Example 27 / 6 = 4.5

27 / 6 = 4.5

4.5 - 4 = 0.5 Get the fractional part

6 * 0.5 = 3 Mul the denominator and fraction

27 mod 6 = 3

Works every time.

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>Works every time.  I'd be worried if it didn't. – 1110101001 Jun 24 at 4:45
No, it doesn't work every time because of limited precision. If you ask for the fractional part of $\frac {10^{50}+1}{10^{50}}$ you get exactly zero on calculators, so your algorithm will give zero for the mod. – Ross Millikan Jun 24 at 4:55

There is a mod function in TI NSpire and any graphing calculator:

Syntax: mod(number to divide, modulus (divisor))

E.g. mod(35^51, 319) Enter yields 167

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