从"常量字符*"到"字符*"的转换无效

#include <stdio.h>
#include <string.h>
#include <conio.h>
#define SIZE 20
int main( void )
{
    int n; //number of characters to be compared
    char s1[ SIZE ], s2[ SIZE ];
    char *results_word;
    printf( "Enter two strings: " );
    gets( s1 );
    gets( s2 );
    printf( "nEnter the number of characters to be compared: " );
    scanf( "%d", &n );

问题从这里开始

    results_word = 
                 strncmp( s1, s2, n ) > 0 ? " greater than " : 
                 strncmp( s1, s2, n ) == 0 ? " equal to " : " smaller than " ;
    printf( "n%sis%s%s", s1, results_word, s2 );
    getche();
    return 0;
}//end function main

那么为什么result_word没有得到相应的字符串呢？