View Compilation Error

0_0_16046679_18101.cpp: In function 'int main()':
0_0_16046679_18101.cpp:6:18: error: 'scanf' was not declared in this scope
     scanf("%d",&n);
                  ^
0_0_16046679_18101.cpp:9:17: error: 'getchar' was not declared in this scope
         getchar();
                 ^
0_0_16046679_18101.cpp:10:15: error: 'gets' was not declared in this scope
         gets(a);
               ^
0_0_16046679_18101.cpp:22:26: error: 'printf' was not declared in this scope
         printf("a:%d\n",A);
                          ^