View Compilation Error

0_0_24947089_15362.cpp: In function 'int main()':
0_0_24947089_15362.cpp:43:29: error: 'scanf_s' was not declared in this scope
  while (scanf_s("%s%s", a, b) && strcmp(a, "#") != 0) {
                             ^
0_0_24947089_15362.cpp:43:47: error: 'strcmp' was not declared in this scope
  while (scanf_s("%s%s", a, b) && strcmp(a, "#") != 0) {
                                               ^
0_0_24947089_15362.cpp:44:22: error: 'strlen' was not declared in this scope
   int len1 = strlen(a);
                      ^