View Compilation Error

0_0_13437695_28755.cpp: In function 'int main()':
0_0_13437695_28755.cpp:4:18: error: 'scanf' was not declared in this scope
     scanf("%d",&t);
                  ^
0_0_13437695_28755.cpp:9:9: error: 'a' was not declared in this scope
         a[2] = 1.0;
         ^
0_0_13437695_28755.cpp:15:42: error: 'printf' was not declared in this scope
         printf("%.0lf%%\n",(a[n]/s)*100.0);
                                          ^