Why the randomize() function not working?

I and my friend are trying to make a "Hangman" game using C++ for our school project. But on compilation, the messages show that the standard functions randomize() and random were not declared in this scope. What is wrong in the code?

#include <iostream>    
#include <cstdlib>
#include <cstring>
#include<cstdio>
using namespace std;
const int MAXLENGTH=80;
const int MAX_TRIES=5;
const int MAXROW=7;

int letterFill (char, char[], char[]);
void initUnknown (char[], char[]);

int main ()
{
  char unknown [MAXLENGTH];
  char letter;
  int wrong_guesses=0;
  char word[MAXLENGTH];
  char words[][MAXLENGTH] =
    {
      "batman begins",
      "superman returns",
      "2012",
      "tarzan",
      "goal",
      "300",
      "space jam",
      "transformers",
      "megamind",
      "spiderman"
        };
     randomize();
     int n=random(10);
     strcpy(word,words[n]);
     initUnknown(word, unknown);

     cout << "\n\nWelcome to hangman...Guess a Movie Name";
     cout << "\n\nEach letter is represented by a star.";
     cout << "\n\nYou have to type only one letter in one try";
     cout << "\n\nYou have " << MAX_TRIES << " tries to try and guess the word.";
     cout << "\n~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~";

     while (wrong_guesses < MAX_TRIES)
      {
       cout << "\n\n" << unknown;
       cout << "\n\nGuess a letter: ";
       cin >> letter;
         if (letterFill(letter, word, unknown)==0)
               {
                 cout << endl << "Whoops! That letter isn't in there!" << endl;
                 wrong_guesses++;
                }
         else
             {
                  cout << endl << "You found a letter! Isn't that exciting!" << endl;
             }

         cout << "You have " << MAX_TRIES - wrong_guesses;
         cout << " guesses left." << endl;
            if (strcmp(word, unknown) == 0)
             {
                cout << word << endl;
               cout << "Yeah! You got it!";
               break;
               }

              }
            if(wrong_guesses == MAX_TRIES)
           {
              cout << "\nSorry, you lose...you've been hanged." << endl;
              cout << "The word was : " << word << endl;
            }
          cin.get();
           return 0;
           }
       int letterFill (char guess, char secretword[], char guessword[])
  {
     int i;
     int matches=0;
    for (i = 0; secretword[i]!='\0'; i++)
   {
   if (guess == guessword[i])
   return 0;
   if (guess == secretword[i])
   {
     guessword[i] = guess;
     matches++;
    }
   }
   return matches;
   }
 void initUnknown (char word[], char unknown[])
  {
  int i;
  int length = strlen(word);
  for (i = 0; i < length; i++)
  unknown[i]='*';
  unknown[i]='\0';
  }