Printing signbit - c

Question

I feel like I am nearing an end on this assignment, but do not understand why it only works correctly every other time. If I enter "FFFFFFFF" my program prints out:
0xFFFFFFFF
signBit 1, expBits 255, fractBits 0x007FFFFF
QNaN
but if I enter "FFFFFFFF" again my program prints out:
0xFFFFFFFF
my program will not print out the correct output every time but yet every other time.
Is there anyone who can help me identify where the error occurs in my code?
Any help is greatly appreciated!
Thanks!
// do not change this code except in the following ways:
// * write code for the following functions:
// * bigOrSmallEndian()
// * getNextHexInt()
// * printLinesForNumber()
// * change studentName by changing "I. Forgot" to your actual name
#include <stdio.h>
#include <stdlib.h>
static char *studentName = "Tenzin Shakya";
// report whether machine is big or small endian
void bigOrSmallEndian()
{
int num = 1;
if(*(char *)&num == 1)
{
printf("\nbyte order: little-endian\n\n");
}
else
{
printf("\nbyte order: big-endian\n\n");
}
}
// get next int (entered in hex) using scanf()
// returns 1 (success) or 0 (failure)
// if call succeeded, return int value via i pointer
int getNextHexInt(int *i)
{
// replace this code with the call to scanf()
//*i = 0;
//return 1;
scanf ("%x", i);
return 1;
}
// print requested data for the given number
void printNumberData(int i)
{
//printf("%x %0#10x\n",i,*(int *)&i);
int tru_exp =0;
//int stored_exp;
int negative;
int exponent;
int mantissa;
printf("\n>");
scanf("%x", &i);
printf("\n0x%08X",i);
negative = !!(i & 0x80000000);
exponent = (i & 0x7f800000) >> 23;
mantissa = (i & 0x007FFFFF);
printf("\nsignBit %d, ", negative);
printf("expbits %d, ", exponent);
printf("fractbits 0x%08X", mantissa);
// "%#010x, ", mantissa);
if(exponent == 0)
{
if(mantissa != 0)
{
printf("\ndenormalized ");
}
}
else{
printf("\nnormalized: ");
tru_exp = exponent - 127;
printf("exp = %d", tru_exp);
}
if(exponent == 0 && mantissa == 0 && negative == 1)
{
printf("\n-zero");
}
if(exponent ==0 && mantissa == 0 && negative == 0)
{
printf("\n+zero");
}
if(exponent == 255 && mantissa != 0 && negative == 1)
{
printf("\nQNaN");
}
if(exponent == 255 && mantissa != 0 && negative == 0)
{
printf("\nSNaN");
}
if(exponent == 0xff && mantissa == 0 && negative == 1)
{
printf("\n-infinity");
}
if(exponent == 0xff && mantissa == 0 && negative == 0)
{
printf("\n+infinity");
}
printf("\n");
while(i != 0)
break;
}
// do not change this function in any way
int main(int argc, char **argv)
{
int i; // number currently being analyzed
int nValues; // number of values successfully parsed by scanf
printf("CS201 - A01p - %s\n\n", studentName);
bigOrSmallEndian();
for (;;) {
if (argc == 1) // allow grading script to control ...
printf("> "); // ... whether prompt character is printed
nValues = getNextHexInt(&i);
printf("0x%08X\n", i);
if (! nValues) { // encountered bad input
printf("bad input\n");
while (getchar() != '\n') ; // flush bad line from input buffer
continue;
}
printNumberData(i);
if (i == 0)
break;
}
printf("\n");
return 0;
}

Answer 1

You are inputting the user's number in getNextHexInt, but printNumberData asks for the input again with another scanf. You don't need the second scanf because the input i is already set to the user's input from getNextHexInt.

Answer 2

here's the code for doing that
float myFloat;
int myInt;
memcpy(&myInt, &myFloat, 4);
int signBit = ((1 << 31) & myInt) >> 31;
printf("%i\n", signBit)
I typed it up in a rush, hopefully it works, ill check it in a sec
Heres a program, but it displays -1 for some reason for sign
#include <string.h>
#include <stdio.h>
int main()
{
float a = 1337;
int* b = (int*)&a;
int signbit = ((1 << 31) & *b) >> 31;
printf("%i\n", signbit);
a *= -1;
signbit = ((1 << 31) & *b) >> 31;
printf("%i\n", signbit);
return 0;
}