Need help with tic tac toe game

[NRoth]

I am in a C++ programming class right now, and I'm stuck. We made a Tic Tac Toe game (as shown below) that needs two players..I would like to change this program, so that Instead of player 2 getting a chance to enter a move, the computer will mark an 'o' and act as player 2. Thank you for your help!

// Include the libraries
#include <iostream>
#include <string>
 
//Use the standard namespace
using namespace std;
 
// Declare global variables
char Board[9];
 
// Declare functions
void showBoard ( );
bool moveIsValid (int m);
int whoWon ( ); //Returns 0 if no one has won, 1 if player 1 has won, and 2 if player 2 has won
 
void main ( )
{
   // Declare local variables
   string Player_1_Name;
   string Player_2_Name;
   int Whose_Turn = 1; // 1 means it's player 1's turn, 2 means it's player 2's turn
   int Move; // Stores where the player wants to move
   int Total_Moves = 0;
 
   //Assign values to the playing board
   Board[0] = '0';
   Board[1] = '1';
   Board[2] = '2';
   Board[3] = '3';
   Board[4] = '4';
   Board[5] = '5';
   Board[6] = '6';
   Board[7] = '7';
   Board[8] = '8';
 
   // Get player names
   cout << "Player 1: Please enter your name." << endl;
   cin >> Player_1_Name;
   cout << "Player 2: Please enter your name." << endl;
   cin >> Player_2_Name;
 
   while (whoWon ( ) == 0 && Total_Moves < 9)
   {
      // Do this until the player chooses a valid move
      do
      {
         // Show the board
         showBoard ( );
 
         // Tell which player to move
         if (Whose_Turn == 1)
         {
            cout << Player_1_Name << ": It's your turn." << endl;
         }
         else
         {
            cout << Player_2_Name << ": It's your turn." << endl;
         }
         // Get the move
         cout << "Enter the number of the spot where you'd like to move." << endl;
         cin >> Move;
      } while (moveIsValid (Move) != true);
 
      // Add 1 to Total_Moves
      Total_Moves++;
 
      // Change whose turn it is
      switch (Whose_Turn)
      {
      case (1):
         {
            Board[Move] = 'x';
            Whose_Turn = 2;
            break;
         }
      case (2):
         {
            Board[Move] = 'o';
            Whose_Turn = 1;
         }
      }
   }
   // Show the board
   showBoard ( );
 
   if (whoWon ( ) == 1)
   {
      cout << Player_1_Name << " has won the game!" << endl;
   }
   else if (whoWon ( ) == 2)
   {
      cout << Player_2_Name << " has won the game!" << endl;
   }
   else
   {
      cout << "It's a tie game!" << endl;
   }
 
   system ("PAUSE");
}
 
void showBoard ( )
{
   cout << endl;
   cout << Board[0] << " | " << Board[1] << " | " << Board[2] << endl;
   cout << "--+---+--" << endl;
   cout << Board[3] << " | " << Board[4] << " | " << Board[5] << endl;
   cout << "--+---+--" << endl;
   cout << Board[6] << " | " << Board[7] << " | " << Board[8] << endl;
   cout << endl;
}
 
bool moveIsValid (int m)
{
   if (Board[m] != 'x' && Board[m] != 'o')
   {
      return true;
   }
   else
   {
      return false;
   }
}
 
int whoWon ( )
{
   if (Board[0] == Board[1] && Board[1] == Board[2])
   {
      if (Board[0] == 'x')
      {
         return 1;
      }
      else
      {
         return 2;
      }
   }
   if (Board[3] == Board[4] && Board[4] == Board[5])
   {
      if (Board[3] == 'x')
      {
         return 1;
      }
      else
      {
         return 2;
      }
   }
   if (Board[6] == Board[7] && Board[7] == Board[8])
   {
      if (Board[6] == 'x')
      {
         return 1;
      }
      else
      {
         return 2;
      }
   }
   if (Board[0] == Board[3] && Board[3] == Board[6])
   {
      if (Board[0] == 'x')
      {
         return 1;
      }
      else
      {
         return 2;
      }
   }
   if (Board[1] == Board[4] && Board[4] == Board[7])
   {
      if (Board[1] == 'x')
      {
         return 1;
      }
      else
      {
         return 2;
      }
   }
   if (Board[2] == Board[5] && Board[5] == Board[8])
   {
      if (Board[2] == 'x')
      {
         return 1;
      }
      else
      {
         return 2;
      }
   }
   if (Board[0] == Board[4] && Board[4] == Board[8])
   {
      if (Board[0] == 'x')
      {
         return 1;
      }
      else
      {
         return 2;
      }
   }
   if (Board[2] == Board[4] && Board[4] == Board[6])
   {
      if (Board[2] == 'x')
      {
         return 1;
      }
      else
      {
         return 2;
      }
   }
   return 0;
}

[Script Coder]

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