View Compilation Error

0_0_23481539_4934.cpp: In function 'int main()':
0_0_23481539_4934.cpp:9:29: error: 'scanf' was not declared in this scope
     while(scanf("%d%d",&n,&k)!=EOF&&((n!=0)||(k!=0)))
                             ^
0_0_23481539_4934.cpp:9:32: error: 'EOF' was not declared in this scope
     while(scanf("%d%d",&n,&k)!=EOF&&((n!=0)||(k!=0)))
                                ^
0_0_23481539_4934.cpp:33:28: error: 'printf' was not declared in this scope
             printf("0.00\n");
                            ^
0_0_23481539_4934.cpp:35:33: error: 'printf' was not declared in this scope
             printf("%.2lf\n",mid);
                                 ^