c programming, how to input a whole number?

zanyzanny · #1 10-Nov-2005, 04:19

Hi,
C programming is one of several modules I'm doing on a course so I won't be too keyed up on it but I have 3 assignments to do. I have the basic program working but what I am after is how to improve it.

I would like to know how can I allow the user to input only whole numbers eg 2, 65, 36, etcetc.

My programme can not work with decimals being inputted and so I would like that if a decimal is inputted that the programme goes through a loop of asking please input a whole number until a whole number is inputted.

So far I have tried making the input a float and then doing the inputted number/1 but using % to look at the remainder (my theory was if remainder is not equal to 0 it is not a whole number so then loop) but then I found this dosent work (i think coz its a float u wouldnt have a remainder but it would just enter the entire number when dividing)

Sorry I have gone on a bit here its a simple question really, how to prevent the user entering non whole numbers.

I do not have access to the code right now and I wouldnt know how to put it up here in a scroll bar thingy, I hope I'm not breaking forum rules too much

hope someone can help

I will keep searching to see if anyone else has asked this question before on this or other websites, so far no such luck tho!

Paramesh · #2 10-Nov-2005, 06:00

Hi Zany,

Welcome to the GID forums.

Instead of telling the user that he has to input only whole numbers, you can ignore the decimal points by just using an integer.

so, get the float input.
Then make an integer equal to the float.
Consider this sample program:

CPP / C++ / C Code:

#include<stdio.h>
int main()
{
    float f;
    int i;
    
    printf("Enter a number(only whole numbers accepted)...");
    scanf("%f",&f);
    
    i = f;
    printf("The whole number is %d \n",i);
    
    return 0;
}

Regards,

Paramesh.

zanyzanny · #3 10-Nov-2005, 06:33

I hadn't thought of it that way round! so even if they put in a decimal it will only look at the whole number part?
thanks i will try this out as soon as i can!

Paramesh · #4 10-Nov-2005, 06:46

Quote:

Originally Posted by Zany

I hadn't thought of it that way round! so even if they put in a decimal it will only look at the whole number part?

Yes.

But there can also be better methods than this one.

Regards,
Paramesh.

Guidelines Plz · #5 10-Nov-2005, 10:23

Quote:

Originally Posted by zanyzanny

I do not have access to the code right now and I wouldnt know how to put it up here in a scroll bar thingy, I hope I'm not breaking forum rules too much

You could try reading the post that tells you how... found easily at the top of the forum thread.

WaltP · #6 10-Nov-2005, 10:28

Quote:

Originally Posted by Paramesh

Instead of telling the user that he has to input only whole numbers, you can ignore the decimal points by just using an integer.

so, get the float input.
Then make an integer equal to the float.

And what happens if the user enters a letter just to be ornery? This info on scanf(). It's part of a series explaining the trouble using scanf() for user-input.

Never underestimate the cruelty of a user

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c programming, how to input a whole number?

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