foo.cpp:3:1: error: 'uisng' does not name a type
 uisng namespace std;
 ^
foo.cpp: In function 'int main()':
foo.cpp:7:4: error: 'cin' was not declared in this scope
    cin>>a>>b;
    ^
foo.cpp:7:4: note: suggested alternative:
In file included from foo.cpp:1:0:
C:/TDM-GCC-32/lib/gcc/mingw32/4.9.2/include/c++/iostream:60:18: note:   'std::cin'
   extern istream cin;  /// Linked to standard input
                  ^
foo.cpp:8:4: error: 'cout' was not declared in this scope
    cout<<a+b;
    ^
foo.cpp:8:4: note: suggested alternative:
In file included from foo.cpp:1:0:
C:/TDM-GCC-32/lib/gcc/mingw32/4.9.2/include/c++/iostream:61:18: note:   'std::cout'
   extern ostream cout;  /// Linked to standard output
                  ^