In standard C, there is no format specifier (such as %d, %x, etc..) to printf that allows printing binary representation of data.

This code snippet shows how to print binary representation of bytes in C.

#include <stdint.h>
#include <stdio.h>
 
void
print_byte(uint8_t byte)
{
        uint8_t         i;
        for (i = 0; i < 8; i++)
                if (byte & (1 << i))
                        printf("1");
                else
                        printf("0");
}
 
 
int
main()
{
 
print_byte(4);
 
return 0;
}

Compile and run to see the binary representation of the integer 4 printed in binary.

 $cc test.c
 $./a.out
  00100000

If you need to display a whole string in binary, simply use the function print_byte for all characters of the string.