gistfile1.c

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

#define INF 1.0/0.0

float calcMinFloat();
float calcFloatErr();
float calcMaxFloat();

int main()
{
        float f;

	f = FLT_MIN;
	printf("Min float %e\n", f);
	f = calcMinFloat();
	printf("Min float calculated %e\n", f);
	f = calcFloatErr();
	printf("Float epsilon = %e\n",f);

	f = FLT_MAX;
	printf("Max float %e\n", f);
	f = calcMaxFloat();
	printf("Max float calculated %e\n", f);

        return 0;
}

float calcMinFloat()
{
	float a,b,c;

	a = 1.0;
	b = 0.0;
	while (a - b != 0.0){
		c = 0.5*(a - b);
		if (c < 0.0){
			b = b - c;
		} else if (c == 0.0) {
			b = a;
		} else {
			a = a -c;
		}
	}
	b = calcFloatErr();
	return a/b;
}

float calcFloatErr()
{
	float err;
	err = 1.0/2.0;
	while ((float) (1.0 + err/2.0) != 1.0){
		err = err / 2.0;
	}

	return err;
}

float calcMaxFloat()
{
	float a, b, err;

	a = b = err = 1.0 + calcFloatErr();
	b = a * err;

	while (b != a && b != INF){
		a = a * err;
		b = a * err;
	}
	return a;
}