View Compilation Error

0_0_15745878_21544.cpp: In function 'int main()':
0_0_15745878_21544.cpp:5:24: error: 'scanf' was not declared in this scope
     while(scanf("%d",&n)!=EOF)
                        ^
0_0_15745878_21544.cpp:5:27: error: 'EOF' was not declared in this scope
     while(scanf("%d",&n)!=EOF)
                           ^
0_0_15745878_21544.cpp:7:17: error: 'getchar' was not declared in this scope
         getchar();
                 ^
0_0_15745878_21544.cpp:11:16: error: 'gets' was not declared in this scope
         gets(ch);
                ^
0_0_15745878_21544.cpp:12:20: error: 'strlen' was not declared in this scope
         m=strlen(ch);
                    ^
0_0_15745878_21544.cpp:32:53: error: 'printf' was not declared in this scope
    printf("a:%d\ne:%d\ni:%d\no:%d\nu:%d\n",a,b,c,d,e);
                                                     ^