Concatenating two strings - strcat() - string.h

#include<string.h>
#include<iostream>
using namespace std;
// Program to convert a string into lower case

main()
{
char str[100],str_small[30];
cout<<"Enter a String 1 ";
cin.getline(str,100);

cout<<"Enter a String 2 ";
cin.getline(str_small,100);

cout<<"\n Entered String 1 = " <<str;
cout<<"\n Entered String 2 = " <<str_small;
strcat(str,str_small);
cout<<"\n Changed String = " <<str;
}