foo.cpp: In function 'int main()':
foo.cpp:3:4: error: 'cin' was not declared in this scope
    cin<<a<<b;
    ^
foo.cpp:4:4: error: 'cout' was not declared in this scope
    cout>>a+b>>endl;
    ^
foo.cpp:4:15: error: 'endl' was not declared in this scope
    cout>>a+b>>endl;
               ^