My solution (print both decimal and binary)

Objective-C Programming (2nd Edition) 38. Bitwise Operations
1

[code]#include <stdio.h>
#include <inttypes.h>

void makeBinary(int64_t n)
{
if (n) {
if (n & 1) {
makeBinary(n >> 1);
printf(“1”);
} else {
makeBinary(n >> 1);
printf(“0”);
}
}
}

void printBinary(int64_t n)
{
makeBinary(n);
printf("\n");
}

int main(int argc, const char * argv[])
{
uint64_t a = 1;
for (int i = 0; i < 64; i++) {
if (i%2) {
a <<= 1;
a |= 1;
} else {
a <<= 1;
}
}

printf("%" PRIu64 "\n", a);

printBinary(a);
    
return 0;

}[/code]

2

printBinary is discriminating against zero. Zero is a perfectly good number.

3

Yes, you’re right! I didn’t consider zero. Here is new printBinary():

[code]void makeBinary(int64_t n, int counter)
{
counter -= 1;
if (counter) {
if (n & 1) {
makeBinary(n >> 1, counter);
printf(“1”);
} else {
makeBinary(n >> 1, counter);
printf(“0”);
}
}
}

void printBinary(int64_t n)
{
makeBinary(n, 64+1);
printf(“\n”);
}[/code]

4

No, that is pretty messy.

This will do the job nicely:

void printBinary (int64_t n)
{
   if (!n) {
        printf ("0");
   }
   else {
        makeBinary (n);
   }
   printf ("\n");
}

Also I would rename makeBinary to make its purpose clear.

For example:

void printBinary (int64_t n)
{
   if (!n) {
        printf ("0");
   }
   else {
       void printBinaryBits (int64_t);
       printBinaryBits (n);
   }
   printf ("\n");
}

void printBinaryBits (int64_t n)
{
    if (n) {
        if (n & 1) {
            printBinaryBits (n >> 1);
            printf ("1");
        } else {
            printBinaryBits (n >> 1);
            printf ("0");
        }
    }
}

[Accelerate your learning and become a competent programmer: pretty-function.org]

5

Hi @abex10, I just did a quick and dirty fix. You really inspired me!