View Compilation Error

0_0_20295506_25319.cpp: In function 'int main()':
0_0_20295506_25319.cpp:5:24: error: 'scanf' was not declared in this scope
     while(scanf("%d",&a)==1)
                        ^
0_0_20295506_25319.cpp:14:26: error: 'printf' was not declared in this scope
         printf("%.0f\n",d);
                          ^
0_0_20295506_25319.cpp:16:16: error: 'system' was not declared in this scope
  system("pause");
                ^