write string reverse program in c

1:  #include <stdio.h>  
2:  #include <string.h>  
3:  void my_strrev(char *str)  
4:  {  
5:    char temp;  
6:    char *start = str;  
7:    char *end = str+strlen(str)-1;  
8:    while(end>start)  
9:    {  
10:      temp = *start;  
11:      *start = *end;  
12:      *end = temp;  
13:      start++;  
14:      end--;  
15:    }  
16:    printf("str = %s\n",str);  
17:  }  
18:  main()  
19:  {  
20:    char str[100] = "hello World";  
21:    my_strrev(str);  
22:    printf("%s\n",str);  
23:  }