#include <stdio.h>
#include <float.h>
//#include <math.h>

static float onef = 1.000000000000000000000e+00;
static double one = 1.000000000000000000000e+00;
static long double onel = 1.00000000000000000000000000000e+00;

int main(void) {
    printf("Size of float = %ld\n",sizeof(float));
    printf("Size of double = %ld\n",sizeof(double));
    printf("Size of long double = %ld\n",sizeof(long double));

    printf("one = %g\n",one);
    float fx=onef*0.1;
    double dx=one*0.1;
    long double ldx=onel*0.1;

    while(one+dx!=one) dx*=0.1;

    printf("DBL_EPSILON = %g\n",DBL_EPSILON);
    printf("DX = %g\n",dx);

    while(onef+fx!=onef) fx*=0.1;

    printf("FLT_EPSILON = %g\n",FLT_EPSILON);
    printf("FX = %g\n",fx);

    while(onel+ldx!=onel) ldx*=0.1;

    printf("LDBL_EPSILON = %g\n",LDBL_EPSILON);
    printf("LDX = %g\n",ldx);

    return 0;
}

// Killy
$ gcc -O2 -o dbl_epsilon dbl_epsilon.c -Wl,-s
23:05:10|<killy tests>
$ ./dbl_epsilon 
Size of float = 4
Size of double = 8
Size of long double = 12
one = 1
DBL_EPSILON = 2.22045e-16
DX = 1e-16
FLT_EPSILON = 1.19209e-07
FX = 1e-08
LDBL_EPSILON = -0
LDX = -2.33511e-15

$ gcc -O0 -o dbl_epsilon dbl_epsilon.c -Wl,-s
23:08:12|<killy tests>
$ ./dbl_epsilon 
Size of float = 4
Size of double = 8
Size of long double = 12
one = 1
DBL_EPSILON = 2.22045e-16
DX = 1e-20
FLT_EPSILON = 1.19209e-07
FX = 1e-20
LDBL_EPSILON = -0
LDX = -2.33511e-15