compile error in this code

[blue_gene]

#include<iostream>
#include<string>
using namespace std;

typedef vector<string> s1;
s1 array;
void func(string x);
void call(string y);

int main()
{
  string str = "abcd";
 if(str == "efg") cout<<"hello"<<endl;
else
 {
 func(str);
  call(str);
 cout<<array[0]<<endl;
 }
}

void func(string x)
{
array.push_back(x);
}

void call(string y)
{
 cout<<"i am here ";
}

i am getting compile error in this code.

i want two things >

1. why there is errors.

2. how can i fix those errors.

[Prelude]

>1. why there is errors.
You forgot to include <vector>.

>2. how can i fix those errors.
Include <vector>