c - 与 c 中的大小相比，为什么 float 的输出包含更多零

Question

#include<stdio.h>
int main()
{
    float a = 1.5;
    printf("%f", a);
    return 0;
}

显示的输出为1.500000。为什么它包含 5 个零？

Answer 1

默认情况下打印时， double (和 float )具有六位精度(小数点后)。

来自 printf(3) 手册页:

The double argument is rounded and converted to decimal notation in the style [-]ddd.ddd, where the number of digits after the decimal-point character is equal to the precision specification. If the precision is missing, it is taken as 6; if the precision is explicitly zero, no decimal-point character appears. If a decimal point appears, at least one digit appears before it.