Stiring Upper & Lower Case

#include<string.h>
int main()
{
    char s[1000], s1, * temp;
    gets(s, s1);

    int len = strlen(s);
    printf("Lenght of the string %d\n", len);

    temp = strlwr(s);
    printf("Lower cased string %s\n", temp);

    temp = strupr(s);
    printf("Upper cased string %s", temp);

    temp = strcat(s, s1);
    printf("Concated string:%s", temp);

    temp = strncat(s, s1, 2);
    printf("Concated string:%s", temp);

}