#include <stdio.h>
#include <math.h>
#include <stdbool.h>

/*************************/
void decToIEEE()
{
	/* declare local variables */
float decimal;
int sign;
int exponent;
int mantissa = 0;
int ieee = 0;

	/* prompt for floating point decimal number */
printf("\nEnter Decimal Representation: ");
scanf("%f", &decimal);

	/* Check for 0--if so, print result */
if (decimal == 0.0)
	printf("\n\nSign: 0\nBiased Exponent: 00000000\nMantissa: 0000000000000000000000\nIEEE-754: 0000 0000\n\n");
else {
		/* Print sign: if number>0, sign is 0, else 1 */
	sign = (decimal > 0) ? 0 : 1;
	printf("\n\nSign: %d\n", sign);

		/* take absolute value of number before generating significand */
	decimal = (decimal < 0) ? decimal*-1 : decimal;

		/* Normalize number:
		while number >2, divide by 2, increment exponent
		while number <1, multiply by 2, decrement exponent
		*/
	exponent = 0;
	while(decimal >= 2) {
		decimal = decimal / 2.0;
		exponent++;
	}

	while(decimal < 1) {
		decimal *= 2.0;
		exponent--;
	}


		    /* Bias exponent by 127 and print each bit in binary with 8-iteration for-loop*/
	exponent += 127;

	printf("Exponent: ");

	float temp_exp = exponent;
	for (int i = 0; i < 8; i++) {
		if (temp_exp > 128) {
			printf("1");
			temp_exp  -= 128;
		}
		else
			printf("0");
		temp_exp *= 2;
	}


    		/* Hide 1 and print significand in binary with 23-iteration for-loop*/
	decimal -= 1; // decrement to remove the 1

	printf("\nMantissa: ");

	float temp_dec = decimal;

	for (int i = 0; i < 23; i++) {
		if (temp_dec < 0.5) {
			printf("0");
			temp_dec *= 2;
		}
		else {
			printf("1");
			temp_dec = temp_dec*2 -1;
		}
	}


		/* Print IEEE-754 representation */
	ieee = sign * pow(2,31) + exponent*pow(2,23) + decimal*pow(2,23);

	printf("\nIEEE format: %x", ieee);

}
  return;
}


/***********************************************************************/
void ieeeToDec()
{
  /* declare local variables */

	int ieee_number;

  /* prompt for IEEE-754 representation */

	printf("\nEnter IEEE-754 Representation: \n");
	scanf("%x", &ieee_number);

	/* check for special cases: 0, -0, +infinity, -infinity, NaN,
		if so, print and return */

	if (ieee_number == 0x00000000) // 0
			printf("Special case: +0\n");
	else if (ieee_number == 0x80000000) // -0
			printf("Special case: -0\n");
	else if(ieee_number == 0x7F800000) // + inf
			printf("Special case: Positive Infinity\n");
	else if(ieee_number == 0xFF800000) // - inf
			printf("Special case: Negative Infinity\n");
	else if ((ieee_number & 0x7FFFFFFF) > (0x7F800000)) // NaN, force the first number to be a 0
			printf("Special case: NaN\n");
	else {

	// FOR OTHER NUMBERS, CHECK POSITIVE OR NEGATIVE AND VALUES WITH MASKING: USING '&' WITH 0's

	/* Mask sign from number: if sign=0, print "+", else print "-" */


	/* Mask biased exponent and significand from number */

	int exp = ((ieee_number & 0x7FFFFFFF) >> 23) - 127;
	float mantissa = ((ieee_number << 9) * pow(2,-32));

	if (ieee_number >> 31 == 0) {
			printf("\nSign: +");
		}
		else {
			printf("\nSign: -");
			mantissa *= -1;
		}

	/* If biased exponent=0, number is denormalized with unbiased exponent of -126,
		print denormalized number as fraction * 2^(-126), return */

	if (exp == -127) {
		printf("\nUnbiased Exponent: -126\nDenormalized Decimal: %f*2^(-126)", mantissa);
	}
	else {
	/* Unbias exponent by subtracting 127 and print */
		printf("\nUnbiased Exponent: %d", exp);
	/* Add hidden 1 and print normalized decimal number */
		printf("\nNormalized decimal: %f", mantissa + 1);
	/* Print decimal number */
		printf("\nDecimal: %f", (mantissa + 1)*pow(2, exp));
	}
}
 return;
}

int main()
{
  /* declare local variables */
int selection;

bool exit = false;
while(!exit) {

	printf("\n\nFloating-point conversion: \n__________________________\n");
	printf("1) Decimal to IEEE-754 conversion \n2) IEEE-754 to Decimal conversion \n3) Exit\n\nEnter Selection: ");

	scanf("%d", &selection);
	switch (selection) {
		case 1: decToIEEE(); break;
		case 2: ieeeToDec(); break;
		case 3: exit = true; break;
	}
}

/* until user chooses to quit, prompt for choice and select appropriate function */

  return 0;
}