View Compilation Error

0_0_24211781_2289.cpp: In function 'int cmp(elem, elem)':
0_0_24211781_2289.cpp:28:36: error: 'strcmp' was not declared in this scope
         return strcmp(a.name,b.name)<0?1:0;  
                                    ^
0_0_24211781_2289.cpp: In function 'trie* newtrie()':
0_0_24211781_2289.cpp:35:39: error: 'memset' was not declared in this scope
         memset(t,0,sizeof(struct trie));     
                                       ^
0_0_24211781_2289.cpp: In function 'int main()':
0_0_24211781_2289.cpp:139:60: error: 'strcpy' was not declared in this scope
                         strcpy(add_str[len_add],stu[i].name);  
                                                            ^
0_0_24211781_2289.cpp:144:60: error: 'strcpy' was not declared in this scope
                         strcpy(del_str[len_del],stu[i].name);  
                                                            ^