C++ program code:

//Header section
#include <iostream>
#include <fstream>
#include <string>
using namespace std;

//The getHighScore function takes a string reference 
//parameter playerName and an integer reference parameter highScore.
void getHighScore(string& playerName, int& highScore)
{
    //Declare variables
    string name;
    int score;
    string highestPlayer;
    int highestScore = 0;
    
    //Opens the file named "scores.txt" using an ifstream object.
    ifstream inputFile("scores.txt");
    //Use a while loop that reads the file line by line, 
    //extracting the player name and score.
    while (inputFile >> name >> score)
    {
        //checks if the current score is higher than the
        //previous highest score. If so, it updates highestPlayer 
        //and highestScore.
        if (score > highestScore) 
        {
            highestPlayer = name;
            highestScore = score;
        }
    }

    inputFile.close();
    //Finally, the function assigns the values of highestPlayer
    //and highestScore to the reference parameters playerName 
    //and highScore, respectively.
    playerName = highestPlayer;
    highScore = highestScore;
}
//Program starts with a main function
int main() 
{
    //Declare variables
    string playerName;
    int highScore;
   //Call the method
    getHighScore(playerName, highScore);
    //Display the name of the player with the highest score
    //and the corresponding score
    cout << "The player with the highest score is: " << playerName << endl;
    cout << "The highest score is: " << highScore << endl;

    return 0;
}

Input file data(scores.txt):

Ronaldo 
10400
Didier 
9800
Pele 
12300
Kaka 
8400
Cristiano 
8000

Output of the program code:

The player with the highest score is: Pele
The highest score is: 12300