Very Simple Noob Request [C++]

  #include<fstream.h>
    int main()
    {
        char str[2000];
        fstream file_op("c:\\test_file.txt",ios::in);
        while(file_op >> str)
        cout << str ;
 
        file_op.close();

        return 0;
    }

ifstream f("test.txt");
f>>n;
f.close();
cout<<n;
cin.get();

1>c:\users\michael\documents\visual studio 2008\projects\combat arm console\combat arm console\combat arm console.cpp(30) : error C2065: 'ifstream' : undeclared identifier
1>c:\users\michael\documents\visual studio 2008\projects\combat arm console\combat arm console\combat arm console.cpp(30) : error C2146: syntax error : missing ';' before identifier 'f'
1>c:\users\michael\documents\visual studio 2008\projects\combat arm console\combat arm console\combat arm console.cpp(30) : error C3861: 'f': identifier not found
1>c:\users\michael\documents\visual studio 2008\projects\combat arm console\combat arm console\combat arm console.cpp(31) : error C2065: 'f' : undeclared identifier
1>c:\users\michael\documents\visual studio 2008\projects\combat arm console\combat arm console\combat arm console.cpp(31) : error C2065: 'n' : undeclared identifier
1>c:\users\michael\documents\visual studio 2008\projects\combat arm console\combat arm console\combat arm console.cpp(32) : error C2065: 'f' : undeclared identifier
1>c:\users\michael\documents\visual studio 2008\projects\combat arm console\combat arm console\combat arm console.cpp(32) : error C2228: left of '.close' must have class/struct/union
1>        type is ''unknown-type''
1>c:\users\michael\documents\visual studio 2008\projects\combat arm console\combat arm console\combat arm console.cpp(33) : error C2065: 'cout' : undeclared identifier
1>c:\users\michael\documents\visual studio 2008\projects\combat arm console\combat arm console\combat arm console.cpp(33) : error C2065: 'n' : undeclared identifier
1>c:\users\michael\documents\visual studio 2008\projects\combat arm console\combat arm console\combat arm console.cpp(34) : error C2065: 'cin' : undeclared identifier
1>c:\users\michael\documents\visual studio 2008\projects\combat arm console\combat arm console\combat arm console.cpp(34) : error C2228: left of '.get' must have class/struct/union
1>        type is ''unknown-type''

ifstream f("test.txt");
f>>n;
f.close();
cin.get();

1>c:\users\michael\documents\visual studio 2008\projects\combat arm console\combat arm console\combat arm console.cpp(34) : error C2061: syntax error : identifier 'n'
1>c:\users\michael\documents\visual studio 2008\projects\combat arm console\combat arm console\combat arm console.cpp(36) : error C2065: 'n' : undeclared identifier

syntax error : missing ';' before identifier 'ifstream'