Saving a value if it is larger than the current value...

I have a score script right here:

using UnityEngine;
using System.Collections;

public class ScoreSystem : MonoBehaviour {
	
	public GUIText guiText;
	public int scoreValue;
	
	public static bool hasPlayed = false;
	
	// Use this for initialization
	void Start () {

	}
	
	// Update is called once per frame
	void Update () {
		if(Move.playerAlive) {
			scoreValue++;
		}
		
		guiText.text = "" + scoreValue;
		
		PlayerPrefs.SetInt("scoreValue", scoreValue);
		
		if(!Move.playerAlive) {
			PlayerPrefs.Save();
			hasPlayed = true;
		}
	}
}

What I want is to have another PlayerPrefs value, that will only record the highest score (high score). Can anyone help me out?

Thanks in advance!

pretty simple, just say:

if(PlayerPrefs.GetInt("High Score") < scoreValue)
PlayerPrefs.SetInt("High Score", scoreValue);

You will need an if statement that checks the current score against the stored highscore:

// at the top
public int highScore;

// in your start functiion
void Start(){
    highScore = PlayerPrefs.GetInt("highScore");
    if (highScore == 0){
        highScore = 0;
    }
}

// in your update function
void Update(){
    // ...
    if (scoreValue > highScore){
        PlayerPrefs.SetInt("highScore", scoreValue);
    } else {
        PlayerPrefs.SetInt("highScore", highScore);
    }
}

I think this as a basic recipe may help you get started.

// Declare variables
private int highScore;
public int scoreValue;

// Use this for initialization 
void Start(){
    if (HasKey("highScore"))
    {
        highScore = PlayerPrefs.GetInt("highScore");
    }else
    {
        PlayerPrefs.SetInt("highScore", 0);
        highScore = 0;
    }      
 }

// Update is called once per frame
void Update(){
    if (scoreValue > highScore){
        PlayerPrefs.SetInt("highScore", scoreValue);
        highScore = scoreValue ;
    } 
}