Could anyone explain the "#x" and output in this code?..

Question

#include <stdio.h>
#define TO_STR(x) #x

int main() {

printf ("%s",TO_STR(123\\45));
return 0;
}

Output:
123\45.

Answer 1

「ＨＡＰＰＹ ＴＯ ＨＥＬＰ」 thnq so much ☺️