View Compilation Error

0_0_26321266_11561.cpp: In function 'int main()':
0_0_26321266_11561.cpp:63:30: error: 'clock' was not declared in this scope
  printf("%.6f\n", 1. * clock() / CLOCKS_PER_SEC);
                              ^
0_0_26321266_11561.cpp:63:34: error: 'CLOCKS_PER_SEC' was not declared in this scope
  printf("%.6f\n", 1. * clock() / CLOCKS_PER_SEC);
                                  ^