how to print memory bits in c

Question

I\'m learning how numbers are represented in memory. I want to know how to print the actual representation (binary or hexadecimal) in memory of some int and float variables.

Answer 1

... to print the actual representation (binary ...

To convert any variable/object to a string that encodes the binary form uses a helper function that converts memory into a "binary" string. This method also handles function pointers. Uses C99 or later.

#include 
#include 
#include 

//                                    .... compound literal .......
#define VAR_TO_STR_BIN(x) obj_to_bin((char [sizeof(x)*CHAR_BIT + 1]){""}, &(x), sizeof (x))

char *obj_to_bin(char *dest, void *object, size_t osize) {
  const unsigned char *p = (const unsigned char *) object;
  p += osize;
  char *s = dest;
  while (osize-- > 0) {
    p--;
    unsigned i = CHAR_BIT;
    while (i-- > 0) {
      *s++ = ((*p >> i) & 1) + '0';
    }
  }
  *s = '\0';
  return dest;
}

int main(void) {
  int i = 42;
  double d = 3.1415926535897932384626433832795;
  printf("Sample\ndouble pi:%s\nint 42:%s\n", VAR_TO_STR_BIN(d), VAR_TO_STR_BIN(i) );
  return 0;
}

Output (Note: depending in endian-ness, results may vary)

Sample
double pi:0100000000001001001000011111101101010100010001000010110100011000  
int 42:00000000000000000000000000101010

This approach is easy to adapt to hexadecimal form.