Как определить диапазоны типов с плавающей точкой с помощью прямого вычисления?

Я пытаюсь решить упражнение 2-1 из "The C Programming Language", 2nd edition, в котором предлагается:

"Напишите программу для определения диапазонов переменных char, short, int и long, как знаковых, так и беззнаковых, путем печати соответствующих значений из стандартных заголовков и путем прямого вычисления. Сложнее, если вы их вычислите: определите диапазоны различных типов с плавающей точкой."

Мне удалось определить диапазоны всех типов, кроме плавающей точки, как с помощью минимальных и максимальных значений из стандартных заголовков, так и путем прямого вычисления.

Как определить диапазоны типов с плавающей точкой с помощью прямого вычисления?

#include <stdio.h>
#include <limits.h>
#include <float.h>

#define TESTBIT 2

/* write a program to determine the ranges of char, short, int, and long variables,
   both signed and unsigned by printing appropriate values from standard headers
   and by direct computation

   harder if you compute them - determine the ranges of the various floating-point types */
main()
{
    char ch, chtest;
    unsigned char uch;
    short sh, shtest;
    unsigned short ush;
    int i, itest;
    unsigned int ui;
    long l, ltest;
    unsigned long ul;
    long long ll, lltest;
    unsigned long long ull;

    ch = uch = sh = ush = i = ui = l = ul = ll = ull = 0;
    ++ch;        /* Maximum and minimum ranges using direct computation */
    chtest = 0;
    while (chtest >= 0) {
        chtest = ch * TESTBIT;
        if (chtest > 0)
            ch = ch * TESTBIT;
    }
    ch = ch * 2;
    printf("Minimum range of signed char variable: %d\n", ch);

    --ch;
    printf("Maximum range of signed char variable: %d\n", ch);

    --uch;
    printf("Maximum range of unsigned char variable: %u\n", uch);

    ++sh;
    shtest = 0;
    while (shtest >= 0) {
        shtest = sh * TESTBIT;
        if (shtest > 0)
            sh = sh * TESTBIT;
    }
    sh = sh * 2;
    printf("Minimum range of signed short variable: %d\n", sh);

    --sh;
    printf("Maximum range of signed short variable: %d\n", sh);

    --ush;
    printf("Maximum range of unsigned short variable: %u\n", ush);

    ++i;
    itest = 0;
    while (itest >= 0) {
        itest = i * TESTBIT;
        if (itest > 0)
            i = i * TESTBIT;
    }
    i = i * 2;
    printf("Minimum range of signed int variable: %d\n", i);

    --i;
    printf("Maximum range of signed int variable: %d\n", i);

    --ui;
    printf("Maximum range of unsigned int variable: %u\n", ui);

    ++l;
    ltest = 0;
    while (ltest >= 0) {
        ltest = l * TESTBIT;
        if (ltest > 0)
            l = l * TESTBIT;
    }
    l = l * 2;
    printf("Minimum range of signed long variable: %d\n", l);

    --l;
    printf("Maximum range of signed long variable: %d\n", l);

    --ul;
    printf("Maximum range of unsigned long variable: %lu\n", ul);

    ++ll;
    lltest = 0;
    while (lltest >= 0) {
        lltest = ll * TESTBIT;
        if (lltest > 0)
            ll = ll * TESTBIT;
    }
    ll = ll * 2;
    printf("Minimum range of signed long long variable: %lld\n", ll);

    --ll;
    printf("Maximum range of signed long long variable: %lld\n", ll);

    --ull;
    printf("Maximum range of unsigned long long variable: %llu\n", ull);

    printf("\nSize of char: %d\n", CHAR_BIT);    /* Max and min ranges using limits.h and float.h header */
    printf("Minimum range of signed char variable: %d\n", SCHAR_MIN);
    printf("Maximum range of signed char variable: %d\n", SCHAR_MAX);
    printf("Maximum range of unsigned char variable: %u\n", UCHAR_MAX);
    printf("Minimum range of signed short variable: %d\n", SHRT_MIN);
    printf("Maximum range of signed short variable: %d\n", SHRT_MAX);
    printf("Maximum range of unsigned short variable: %u\n", USHRT_MAX);
    printf("Minimum range of int variable: %d\n", INT_MIN);
    printf("Maximum range of int variable: %d\n", INT_MAX);
    printf("Maximum range of unsigned int variable: %u\n", UINT_MAX);
    printf("Minimum range of signed long variable: %ld\n", LONG_MIN);
    printf("Maximum range of signed long variable: %ld\n", LONG_MAX);
    printf("Maximum range of unsigned long variable: %lu\n", ULONG_MAX);
    printf("Minimum range of long long variable: %lld\n", LLONG_MIN);
    printf("Maximum range of long long variable: %lld\n", LLONG_MAX);
    printf("Maximum range of unsigned long long variable: %llu\n\n", ULONG_LONG_MAX);
    printf("Minimum range of float variable: %f\n", FLT_MIN);
    printf("Maximum range of float variable: %f\n", FLT_MAX);
    printf("Minimum range of double variable: %f\n", DBL_MIN);
    printf("Maximum range of double variable: %f\n", DBL_MAX);
    printf("Minimum range of long double variable: %lf\n", LDBL_MIN);
    printf("Maximum range of long double variable: %lf\n", LDBL_MAX);
    return 0;
}