浮点不能准确地打印

问题描述

#include<stdio.h>
main()
{
        int a,b;
        float f;
        scanf("%2d%3d%4f",&a,&b,&f);
        printf("%d %d %f",a,b,f);
}

When i run this program and input 2 4 56.8 ,it gives output 2 4 56.799999.....but I would expect 2 4 56.8....why is it so???

解决方案

That is correct. Floating point numbers are approximations. Just as 0.33333333 is an approximation to 1/3, 56.7999999 is an approximation for 56.8. There is no exact floating point representation for 0.1.

See some of what has been written:

• http://docs.oracle.com/cd/E19957-01/806-3568/ncg_goldberg.html
• http://www.hack3r.com/forum-topic/what-every-programmer-should-know-about-floating-point-arithmetic

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