Examine binary representations of floating point numbers on your machine

floperation.c

/* Compile with gcc -Wall -o floperation floperation.c -lquadmath*/

/* Examine binary representations of floating point numbers
   on your machine
   Project Crew 8/10/2024 */

//#include <immintrin.h>
#include <quadmath.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>

#define FLOAT_TYPE   double
#define DESC        "double"
#define INT_TYPE     char

void
int2bin (INT_TYPE myint[], size_t sizeofp, char retstr[])
{
    int c;  // counter
    
    for (c = 7; c > -1; c--)
    {
        //printf("%i", c);
        retstr[c]  = (myint[0] & 1) ? *"1" : *"0";  // test each bit
        myint[0] >>= 1;                             // shift in next bit
    }
    //puts("");
    return;
}

void
trouble (void)
{
    puts("I had trouble printing that.");
    exit (EXIT_FAILURE);
}

int
main (int argc, char **argv)
{
    size_t floatsz                  = sizeof(FLOAT_TYPE);       // size in bytes on current machine
    char   nbytes                   = floatsz;
    char   strout[]                 = { [0 ... 130] = 0 };      // initialize output string to 0
    char   buf[80]                  = { [0 ... 79]  = 0 };
    int    c, d;
    
    
    if(argc == 2)
    {  // keep going...
        union flotion
        {
            INT_TYPE   i[nbytes];
            FLOAT_TYPE f;  // fp variable holding _the number_
        }flote;
        
        flote.f = strtod(argv[1], NULL);
        
        /*FLOAT_TYPE  floteval         =  strtoflt128(argv[1], NULL);  // fp variable holding _the number_
        FLOAT_TYPE *floteptr         = &floteval;                    // initial pointer
        uint8_t   (*flote) [nbytes]  = (uint8_t (*)[])floteptr;      // convert it to unsigned int
        INT_TYPE  (*floteh)[2]       = (INT_TYPE (*)[])*flote;       // buffer to hold working copy of data
        */
        floatsz *= 8;  // get number of bits
        nbytes--;      // account for 0th element in array

        /*quadmath_snprintf (buf, sizeof buf, "%Qf",
            *floteptr);
        */
        d = sprintf(buf, "%f 0x", flote.f);
        if (d < 2) trouble();
        for (c = nbytes; c > 0; c--)
        {
            if (sprintf(&buf[d], "%hhX", flote.i[c]) < 2) trouble();
            d += 2;
        }
        printf ("%s (%zi-bit " DESC ")\n\n",
            buf, floatsz);
        floatsz--;      // decrement to account for 0 bit
        
//        *flote = 38;  // debug
        for (c = nbytes; c > 0; c--)
        {
            //printf("%i", c);
            int2bin(&flote.i[c], floatsz, strout);
            if (printf("%s", strout) < 2) trouble();           // final result of binary conversion
        }
        puts("");
//        printf("%zi", sizeof(unsigned long long int));
                                 // how we doing?
        return(0);
    }else
    {
        puts ("Did you know something about floating point numbers?");  // boiler plate
        puts ("open floperation.c in a text editor, change FLOAT_TYPE and recompile");  // lorem ipsum
        puts ("..\n");
        puts ("floperation displays floating point numbers supported on your system");
        puts ("Usage: floperation XX.XXXXXX where X is some number");
        puts ("Example: floperation 53.33333333333333");
        puts ("Output depends on the type of float being displayed");

        return (1);
    }
}