Converting and implementing endianness in the C language.

In C language, the endianness conversion can be implemented using the following method:

1. Transforming through the use of a union.

#include <stdio.h>

union endian_converter {
   int i;
   char c[sizeof(int)];
};

int main() {
   union endian_converter converter;
   converter.i = 1;

   if(converter.c[0] == 1)
      printf("Little endian\n");
   else
      printf("Big endian\n");

   return 0;
}

In this example, we store an integer 1 in the integer type of a union and use the union’s character array member to check the stored byte order. If the first byte is 1, it indicates storage in little-endian byte order; otherwise, it indicates big-endian byte order.

1. Convert using bitwise operations:

#include <stdio.h>

int main() {
   unsigned int num = 1;
   char *ptr = (char*)&num;

   if(*ptr == 1)
      printf("Little endian\n");
   else
      printf("Big endian\n");

   return 0;
}

In this example, we convert the address of an integer 1 to a character pointer and determine the byte order by checking the value of the byte that the pointer points to. If the first byte is 1, it indicates that it is stored in little-endian byte order; otherwise, it is stored in big-endian byte order.

Both methods can determine endianness on different machines, with the first method using a union and the second method directly manipulating pointers, making it possibly more common.