View Compilation Error

1_733_2682_26068.cpp: In function 'int main()':
1_733_2682_26068.cpp:2:56: error: 'clock' was not declared in this scope
 #define showtime fprintf(stderr,"time = %.15f\n",clock() / (double)CLOCKS_PER_SEC)
                                                        ^
1_733_2682_26068.cpp:120:5: note: in expansion of macro 'showtime'
     showtime;
     ^
1_733_2682_26068.cpp:2:68: error: 'CLOCKS_PER_SEC' was not declared in this scope
 #define showtime fprintf(stderr,"time = %.15f\n",clock() / (double)CLOCKS_PER_SEC)
                                                                    ^
1_733_2682_26068.cpp:120:5: note: in expansion of macro 'showtime'
     showtime;
     ^