View Compilation Error

0_0_21817658_22032.cpp: In function 'void format(char*)':
0_0_21817658_22032.cpp:36:30: error: 'strlen' was not declared in this scope
  int i=0,j,len=0,n=strlen(dst);
                              ^
0_0_21817658_22032.cpp:37:12: error: 'strlwr' was not declared in this scope
  strlwr(dst);
            ^
0_0_21817658_22032.cpp: In function 'int main()':
0_0_21817658_22032.cpp:71:36: error: 'strcpy' was not declared in this scope
    strcpy(text[i].low,text[i].title);
                                    ^
0_0_21817658_22032.cpp:93:31: error: 'strstr' was not declared in this scope
     if (strstr(text[j].low,src))
                               ^