double转16进制科学记数
double 5.67转16进制浮点数
测试程序
/// @file topic1.c
/// @brief test on vs6 cl and link
/// 5.67 double值转16进制科学记数法
#include
#include
void clear_input_buffer();
int main(int argc, char* argv[])
{
int iIndex = 0;
double fIn = 5.67;
/// 想验证下，进程中的变量地址对应的16进制浮点数的具体值
/// 然后在手工运算, 这样就知道自己算得对不对
printf("&fIn = %08x, fIn = %f\r\n", &fIn, fIn);
for (iIndex = 7; iIndex >= 0; iIndex--)
{
printf("%.2x ", (unsigned char)(*((unsigned char*)&fIn + iIndex)));
}
printf("\n");
/** run result
&fIn = 0012ff78, fIn = 5.670000
40 16 ae 14 7a e1 47 ae
*/
/// 40 16 ac 00 00 00 00 00 这是我算出来的 5.76 double, 精度是小数点后8位
/// 看看和电脑算的差多少.
printf("please use winhex to modify fIn value, then press any key to continue\n");
system("pause");
printf("&fIn = %08x, fIn = %f\r\n", &fIn, fIn);
printf("END, press any key to quit\n");
getchar();
return 0;
}
void clear_input_buffer()
{
char ch = '\0';
/// scanf 的回车 0x0a, 留在了buffer里面, 用getchar()还能读的到,
/// clear input buffer
do
{
ch = getchar();
} while ((ch != EOF) && (ch != '\n'));
}
手工演算
/// * 5.67 double值转16进制科学记数法
5.67 = 5 + 0.67 = 101.10101011B = 1.0110101011B*10B^2
5 = 101B
0.67 = 10101011B
0.67*2 = 0.34 1
0.34*2 = 0.68 0
0.68*2 = 0.36 1
0.36*2 = 0.72 0
0.72*2 = 0.44 1
0.44*2 = 0.88 0
0.88*2 = 0.76 1
0.76*2 = 0.52 1
S = 0
E = 1023 + 2 = 1025 = 10000000001B
D = 0110101011 0000000000 0000000000 0000000000 0000000000 00
0 10000000001 0110101011 0000000000 0000000000 0000000000 0000000000 00
0100000000010110101011000000000000000000000000000000000000000000
0100,0000,0001,0110,1010,1100,0000,0000,0000,0000,0000,0000,0000,0000,0000,0000
4 0 1 6 a C 0 0 0 0 0 0 0 0 0 0
4 016a C0000000000
虽然和电脑算的（40 16 ae 14 7a e1 47 ae）不一样，但是我的精度只有小数点后8位2进制数. 我用WinHex将电脑算出的double值，换成我的, 看看和5.67差多少
/// 实验证明：我算的是对的
D:\ls\2015_1022\Topic1>call topic1.exe
&fIn = 0012ff78, fIn = 5.670000
40 16 ae 14 7a e1 47 ae
please use winhex to modify fIn value, then press any key to continue
请按任意键继续. . .
&fIn = 0012ff78, fIn = 5.667969
END, press any key to quit