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Editorial Team
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Asked: 2026-05-27T11:50:57+00:00

#include stdafx.h #include stdio.h #include math.h int main() { float c; printf(Type c); scanf(%f,

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#include "stdafx.h"
#include "stdio.h"
#include "math.h"

int main()
{
float c;

printf("Type c");

scanf("%f", &c);


    printf("C is c: %f ",c);

    while(getchar()!='\n');
    getchar();
    return 0;

    }

Very simple code, I just started with C.
With most numbers works ok but for example if I input 47.2 then It prints me 47.200001 with 88.4321 outputs 88.432098
but with other numbers like 5.4 works ok 5.400000
I am using Microsoft Visual Studio 10.

Another thing if the above code instead of putting float c I put double I am not able to printf What should I put instead of %f?
But It worries me more my first question, maybe It is something to do with the compiler maybe I am compiling c code as c++, I dont know.

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1 Answer

  1. Editorial Team

    Regarding your numeric accuracy. This is a known problem when storing floating point values in a binary format. Modified slightly from PHP docs…

    Floating point numbers have limited precision. Although it depends on the system, most languages typically uses the IEEE 754 double precision format, which will give a maximum relative error due to rounding in the order of 1.11e-16. Non elementary arithmetic operations may give larger errors, and, of course, error progragation must be considered when several operations are compounded.

    Additionally, rational numbers that are exactly representable as floating point numbers in base 10, like 0.1 or 0.7, do not have an exact representation as floating point numbers in base 2, which is used internally, no matter the size of the mantissa. Hence, they cannot be converted into their internal binary counterparts without a small loss of precision. This can lead to confusing results: for example, floor((0.1+0.7)*10) will usually return 7 instead of the expected 8, since the internal representation will be something like 7.9999999999999991118….

    So never trust floating number results to the last digit, and never compare floating point numbers for equality.

    If you need better precision you may have to investigate supplementary libraries whose sole purpose is to deal with highly precise numbers.

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