编写C++代码实现二进制浮点数输入，显示其十进制数值结果，所有5类(可 以是0，非正规化数，正规化数，无穷，NaN)浮点结果都要进行测试和结果显示输入为一个32位的数据表示一个32位的二进制浮点数

Question

编写C++代码实现二进制浮点数输入，显示其十进制数值结果，所有5类(可以是0，非正规化数，正规化数，无穷，NaN)浮点结果都要进行测试和结果显示。输入为一个32位的数据表示一个32位的二进制浮点数

Answer 1

仅供参考：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main() {
    float f;
    double d;
    char bs[65];
    char b[65];
    char s[80];
    unsigned char *p;
    char e[12];
    char *t;
    int ex;
    int flag;

    flag=0;
    while (1) {
        printf("Input a float point number or 0xXXXXXXXX or 0xXXXXXXXXXXXXXXXX:");fflush(stdout);
        rewind(stdin);
        fgets(s,80,stdin);
        if ('\n'==s[0]) return 1;
        if (1==sscanf(s,"0x%16I64X",(__int64 *)&d) && strlen(s)>11) {flag=2;break;}
        if (1==sscanf(s,"0x%8X"    ,(  int   *)&f))                 {flag=1;break;}
        if (1==sscanf(s,"%f"       ,           &f)
         && 1==sscanf(s,"%lf"      ,           &d))                 {flag=3;break;}
    }
    if (flag&1) {
        printf("f=%g\n",f);
        p=(unsigned char *)&f;
        printf("hex=%02X %02X %02X %02X\n",p[3],p[2],p[1],p[0]);
        ltoa(*(long *)&f,b,2);
        sprintf(bs,"%032s",b);
        printf("bin=%s\n",bs);
        printf("bin=%.1s %.8s   %s\n",bs,bs+1,bs+9);
        strncpy(e,bs+1,8);e[8]=0;
        ex=strtol(e,&t,2);
        printf("    %c %-4d-127 1.%s\n",(bs[0]=='0')?'+':'-',ex,bs+9);
        ex-=127;
        printf("    %c %-8d 1.%s\n",(bs[0]=='0')?'+':'-',ex,bs+9);
    }
    if (flag&2) {
        printf("\nd=%lg\n",d);
        p=(unsigned char *)&d;
        printf("hex=%02X %02X %02X %02X %02X %02X %02X %02X\n",p[7],p[6],p[5],p[4],p[3],p[2],p[1],p[0]);
        _i64toa(*(__int64 *)&d,b,2);
        sprintf(bs,"%064s",b);
        printf("bin=%s\n",bs);
        printf("bin=%.1s %.11s   %s\n",bs,bs+1,bs+12);
        strncpy(e,bs+1,11);e[11]=0;
        ex=strtol(e,&t,2);
        printf("    %c %-6d-1023 1.%s\n",(bs[0]=='0')?'+':'-',ex,bs+12);
        ex-=1023;
        printf("    %c %-11d 1.%s\n",(bs[0]=='0')?'+':'-',ex,bs+12);
    }

    return 0;
}
//Input a float point number or 0xXXXXXXXX or 0xXXXXXXXXXXXXXXXX:0x3FC0000000000000
//
//d=0.125
//hex=3F C0 00 00 00 00 00 00
//bin=0011111111000000000000000000000000000000000000000000000000000000
//bin=0 01111111100   0000000000000000000000000000000000000000000000000000
//    + 1020  -1023 1.0000000000000000000000000000000000000000000000000000
//    + -3          1.0000000000000000000000000000000000000000000000000000
//
//Input a float point number or 0xXXXXXXXX or 0xXXXXXXXXXXXXXXXX:0x3E000000
//
//f=0.125
//hex=3E 00 00 00
//bin=00111110000000000000000000000000
//bin=0 01111100   00000000000000000000000
//    + 124 -127 1.00000000000000000000000
//    + -3       1.00000000000000000000000
//
//Input a float point number or 0xXXXXXXXX or 0xXXXXXXXXXXXXXXXX:0.125
//f=0.125
//hex=3E 00 00 00
//bin=00111110000000000000000000000000
//bin=0 01111100   00000000000000000000000
//    + 124 -127 1.00000000000000000000000
//    + -3       1.00000000000000000000000
//
//d=0.125
//hex=3F C0 00 00 00 00 00 00
//bin=0011111111000000000000000000000000000000000000000000000000000000
//bin=0 01111111100   0000000000000000000000000000000000000000000000000000
//    + 1020  -1023 1.0000000000000000000000000000000000000000000000000000
//    + -3          1.0000000000000000000000000000000000000000000000000000
//
//Input a float point number or 0xXXXXXXXX or 0xXXXXXXXXXXXXXXXX:
//

// https://docs.microsoft.com/en-us/cpp/c-runtime-library/format-specification-syntax-printf-and-wprintf-functions?view=vs-2019
// https://docs.microsoft.com/zh-cn/cpp/porting/visual-cpp-change-history-2003-2015?view=vs-2019
//
// Starting in Visual Studio 2015, if the argument that corresponds to a floating-point conversion specifier (a, A, e, E, f, F, g, G) is infinite,
// indefinite, or NaN, the formatted output conforms to the C99 standard. This table lists the formatted output:
//   Value           Output
//   --------------  ---------
//   infinity        inf
//   Quiet NaN       nan
//   Signaling NaN   nan(snan)
//   Indefinite NaN  nan(ind)
// Any of these values may be prefixed by a sign. If a floating-point type conversion specifier character is a capital letter,
// then the output is also formatted in capital letters. For example, if the format specifier is %F instead of %f, an infinity
// is formatted as INF instead of inf. The scanf functions can also parse these strings, so these values can make a round trip
// through printf and scanf functions.
//
// Before Visual Studio 2015, the CRT used a different, non-standard format for output of infinite, indefinite, and NaN values:
//   Value                           Output
//   ------------------------------  -------------------------
//   + infinity                      1.#INF random-digits
//   - infinity                      -1.#INF random-digits
//   Indefinite (same as quiet NaN)  digit .#IND random-digits
//   NaN                             digit .#NAN random-digits
// Any of these may have been prefixed by a sign, and may have been formatted slightly differently depending on field width and precision,
// sometimes with unusual effects. For example, printf("%.2f\n", INFINITY) would print 1.#J because the #INF would be "rounded" to 2 digits of precision.
#include <stdio.h>
#include <float.h>
int main() {
    int r;
    double d1=-1.0,d2=-2.0;
    printf("input two double (d1 d2):");
    r=scanf("%lf%lf",&d1,&d2);
    printf("scanf return:%d d1:%lg d2:%lg\n",r,d1,d2);
    printf("_finite(d1):%d\n",_finite(d1));
    printf("_fpclass(d1):0x%04X\n",_fpclass(d1));
    return 0;
}
// input two double (d1 d2):nan 22
// scanf return:2 d1:nan d2:22
// _finite(d1):0
// _fpclass(d1):0x0002
//
// input two double (d1 d2):nan(snan) 22
// scanf return:2 d1:nan(snan) d2:22
// _finite(d1):0
// _fpclass(d1):0x0002
//
// input two double (d1 d2):nan(ind) 22
// scanf return:2 d1:-nan(ind) d2:22
// _finite(d1):0
// _fpclass(d1):0x0002
//
// input two double (d1 d2):-inf 22
// scanf return:2 d1:-inf d2:22
// _finite(d1):0
// _fpclass(d1):0x0004