View Compilation Error

0_0_30124091_3843.cpp: In function 'int main()':
0_0_30124091_3843.cpp:2:14: error: 'scanf' was not declared in this scope
 scanf("%d",&t); 
              ^
0_0_30124091_3843.cpp:6:9: error: 'cin' was not declared in this scope
         cin>>n;
         ^
0_0_30124091_3843.cpp:8:33: error: 'memset' was not declared in this scope
         memset(ans,0,sizeof(ans));
                                 ^
0_0_30124091_3843.cpp:31:42: error: 'printf' was not declared in this scope
        printf("%d %.2lf\n",id,1.0/(res+1));    }
                                          ^