How to fix error BCE0005: Unknown identifier

I’m making a zombie apocalypse game. I copied some code from http://www.instructables.com/id/Intro-to-Unity/step13/HUD-and-Menu-system/ and http://www.instructables.com/id/Intro-to-Unity/step7/LockHide-Cursor/. Then 3 errors popped up:

Assets/scripts/Menu.js(24,5): BCE0005: Unknown identifier: ‘DrawCrosshair’.

DrawCrosshair();

Assets/scripts/Menu.js(36,38): BCE0005: Unknown identifier: ‘Player’.

var health = player.GetComponent(Player).Health;

Assets/scripts/Menu.js(47,5): BCE0005: Unknown identifier: ‘DrawCrosshair’.

DrawCrosshair();

Here is all of the code:

 // True if the menu is open and mouse is unlocked
var MenuOpen : boolean = false;

function Start () {
    UpdateCursorLock();
}

function Update() {
    // Check whether the menu button was released
    if (Input.GetButtonUp("MenuOpen")) {
        MenuOpen = !MenuOpen;
        UpdateCursorLock();
    }
}

// Called each time the Gui needs to be drawn
 // Called each time the Gui needs to be drawn
function OnGUI () {
    if (!MenuOpen) {
        DrawHUD();
    } else {
        DrawMenu();
    }
    DrawCrosshair();
}

function UpdateCursorLock() {
    Screen.lockCursor = !MenuOpen;
    Screen.showCursor = MenuOpen;
}

 function DrawHUD() {
    
    // Get the health from the player
    var player = GameObject.Find("Player");
    var health = player.GetComponent(Player).Health;

    // Position
    var left = 10;
    var top = 10;
    var width = 100;
    var height = 25;
    
    // Make a background box
    GUI.Box (Rect (left, top, width, height), "Health: " + health);
    
    DrawCrosshair();
}

// Draw the menu
function DrawMenu() {
    var centerX = Screen.width/2;
    var centerY = Screen.height/2;
    
    // location of the menu
    var menuLeft = centerX - 50;
    var menuTop = centerY - 50;
    var menuWidth = 100;
    var menuHeight = 100;
    
    var buttonX = menuLeft + 10;
    var buttonWidth = 80;
    var buttonHeight = 20;
    var buttonDist = 25; // distance between each button
    
    // Make a background box
    GUI.Box (Rect (menuLeft, menuTop,menuWidth,menuHeight), "Menu");
    
    // Start / Resume
    if (GUI.Button (Rect (buttonX,menuTop + 1 * buttonDist,buttonWidth,buttonHeight), "Resume")) {
        MenuOpen = false;
        UpdateCursorLock();
    }
    
    // Restart
    if (GUI.Button (Rect (buttonX,menuTop + 2 * buttonDist,buttonWidth,buttonHeight), "Restart")) {
        Application.LoadLevel(Application.loadedLevel);
    }
    
    // Quit (Only works in the Build. Does not work in the eidtor!)
    if (GUI.Button (Rect (buttonX,menuTop + 3 * buttonDist,buttonWidth,buttonHeight), "Quit")) {
        Application.Quit();
    }
}

you are missing some functions. look for code parts start look like this:

function DrawCrosshair() {

some code....

}