Chapter 2, float data type, 5 

>cat float5.c
#include <stdio.h>
void printfloat(float);

main()
{
    float x;
    int i;
    printf("\n          Dec        Hex  +-  exp+127 1.     fraction\n\n");

    x = 1;
    for (i = 1; i < 124; i++)
        x = x*2.0;
    for (i = 125; i < 133; i++) {
        x = x*2.0;
        printfloat(x);
    }
    printf("\n");
    x = 1;
    for (i = 1; i < 124; i++)
        x = x/2.0;
    for (i = 125; i < 155; i++) {
        x = x/2.0;
        printfloat(x);
    }
}
void printfloat(float x)
{
    unsigned long i;
    union floatandlong {
        float asfloat;
        long  aslong;
    } bits32;
    bits32.asfloat = x;
    printf(" %12.5g   %8.8x   ", bits32.asfloat, bits32.aslong);
    for (i = 0x80000000ul; i > 0; i>>=1) {
        if (i == 0x40000000ul)
            printf(" "); 
        if (i == 0x00400000ul)
            printf("   "); 
        printf("%c", (i & bits32.aslong ? '1' : '0')); 
    } 
    printf("\n");
}
unix> gcc float5.c
unix> ./a.out

          Dec        Hex  +-  exp+127 1.     fraction

   2.1268e+37   7d800000   0 11111011   00000000000000000000000
   4.2535e+37   7e000000   0 11111100   00000000000000000000000
   8.5071e+37   7e800000   0 11111101   00000000000000000000000
   1.7014e+38   7f000000   0 11111110   00000000000000000000000
          inf   7f800000   0 11111111   00000000000000000000000
          inf   7f800000   0 11111111   00000000000000000000000
          inf   7f800000   0 11111111   00000000000000000000000
          inf   7f800000   0 11111111   00000000000000000000000

    4.702e-38   01800000   0 00000011   00000000000000000000000
    2.351e-38   01000000   0 00000010   00000000000000000000000
   1.1755e-38   00800000   0 00000001   00000000000000000000000
   5.8775e-39   00400000   0 00000000   10000000000000000000000
   2.9387e-39   00200000   0 00000000   01000000000000000000000
   1.4694e-39   00100000   0 00000000   00100000000000000000000
   7.3468e-40   00080000   0 00000000   00010000000000000000000
   3.6734e-40   00040000   0 00000000   00001000000000000000000
   1.8367e-40   00020000   0 00000000   00000100000000000000000
   9.1835e-41   00010000   0 00000000   00000010000000000000000
   4.5918e-41   00008000   0 00000000   00000001000000000000000
   2.2959e-41   00004000   0 00000000   00000000100000000000000
   1.1479e-41   00002000   0 00000000   00000000010000000000000
   5.7397e-42   00001000   0 00000000   00000000001000000000000
   2.8699e-42   00000800   0 00000000   00000000000100000000000
   1.4349e-42   00000400   0 00000000   00000000000010000000000
   7.1746e-43   00000200   0 00000000   00000000000001000000000
   3.5873e-43   00000100   0 00000000   00000000000000100000000
   1.7937e-43   00000080   0 00000000   00000000000000010000000
   8.9683e-44   00000040   0 00000000   00000000000000001000000
   4.4842e-44   00000020   0 00000000   00000000000000000100000
   2.2421e-44   00000010   0 00000000   00000000000000000010000
    1.121e-44   00000008   0 00000000   00000000000000000001000
   5.6052e-45   00000004   0 00000000   00000000000000000000100
   2.8026e-45   00000002   0 00000000   00000000000000000000010
   1.4013e-45   00000001   0 00000000   00000000000000000000001
            0   00000000   0 00000000   00000000000000000000000
            0   00000000   0 00000000   00000000000000000000000
            0   00000000   0 00000000   00000000000000000000000
            0   00000000   0 00000000   00000000000000000000000
unix>