View Compilation Error

0_0_18115850_22712.cpp: In function 'int main()':
0_0_18115850_22712.cpp:13:2: error: 'thread' was not declared in this scope
  thread t1(hi);
  ^
0_0_18115850_22712.cpp:14:2: error: 't1' was not declared in this scope
  t1.join();
  ^