C reverse bits in unsigned integer

Question

I\'m converting an unsigned integer to binary using bitwise operators, and currently do integer & 1 to check if bit is 1 or 0 and output, then right shift by 1 to divide

Answer 1

You could reverse the bits like you output them, and instead store them in another integer, and do it again :

for (i = 0; i < (sizeof(unsigned int) * CHAR_BIT); i++)
{
  new_int |= (original_int & 1);
  original_int = original_int >> 1;
  new_int = new_int << 1;
}

Or you could just do the opposite, shift your mask :

unsigned int mask = 1 << ((sizeof(unsigned int) * CHAR_BIT) - 1);
while (mask > 0)
{
  bit = original_int & mask;
  mask = mask >> 1;
  printf("%d", (bit > 0));
}

If you want to remove leading 0's you can either wait for a 1 to get printed, or do a preliminary go-through :

unsigned int mask = 1 << ((sizeof(unsigned int) * CHAR_BIT) - 1);
while ((mask > 0) && ((original_int & mask) == 0))
  mask = mask >> 1;
do
{
  bit = original_int & mask;
  mask = mask >> 1;
  printf("%d", (bit > 0));
} while (mask > 0);

this way you will place the mask on the first 1 to be printed and forget about the leading 0's

But remember : printing the binary value of an integer can be done just with printf