View Compilation Error

0_0_30964248_14016.cpp: In function 'int cmp(elem, elem)':
0_0_30964248_14016.cpp:28:30: error: 'strcmp' was not declared in this scope
  return strcmp(a.name, b.name) < 0 ? 1 : 0;
                              ^
0_0_30964248_14016.cpp: In function 'trie* newtrie()':
0_0_30964248_14016.cpp:35:34: error: 'memset' was not declared in this scope
  memset(t, 0, sizeof(struct trie));
                                  ^
0_0_30964248_14016.cpp: In function 'int main()':
0_0_30964248_14016.cpp:139:42: error: 'strcpy' was not declared in this scope
      strcpy(add_str[len_add], stu[i].name);
                                          ^
0_0_30964248_14016.cpp:144:42: error: 'strcpy' was not declared in this scope
      strcpy(del_str[len_del], stu[i].name);
                                          ^