View Compilation Error

0_0_35110479_11366.cpp: In function 'int main()':
0_0_35110479_11366.cpp:28:23: error: 'strlen' was not declared in this scope
             l=strlen(a);
                       ^
0_0_35110479_11366.cpp:40:59: error: 'strcmp' was not declared in this scope
                             if(strcmp(name[k],per[kk].name)==0)
                                                           ^
0_0_35110479_11366.cpp:43:75: error: 'strcpy' was not declared in this scope
                         {per[kk].x=name_k;strcpy(name[name_k],per[kk].name);name_k++;}
                                                                           ^
0_0_35110479_11366.cpp:62:42: error: 'strcmp' was not declared in this scope
             if(strcmp("Erdos, P.",name[i])==0) {start=i;break;}
                                          ^
0_0_35110479_11366.cpp:68:36: error: 'strcmp' was not declared in this scope
                 if(strcmp(a,name[j])==0) {end=j;break;}
                                    ^
0_0_35110479_11366.cpp:70:39: error: 'memset' was not declared in this scope
             memset(flag,0,sizeof(flag));    
                                       ^