View Compilation Error

0_0_26839493_32130.cpp: In function 'int main()':
0_0_26839493_32130.cpp:5:19: error: 'scanf' was not declared in this scope
     scanf("%d", &t);
                   ^
0_0_26839493_32130.cpp:9:27: error: 'strlen' was not declared in this scope
         int len=strlen(str);
                           ^
0_0_26839493_32130.cpp:37:50: error: 'printf' was not declared in this scope
                          printf("**%d %d\n",i,  a);
                                                  ^
0_0_26839493_32130.cpp:45:27: error: 'printf' was not declared in this scope
         printf("%d\n", sum);
                           ^