Ok, i think i finally got it what you mean ;)

Well there are many ways to do something like that. Usually you would just use simple trigonometry.

Since you didn't specify a language and you didn't posted any code related questions before, i will use C#

//C#
void OnGUI()
{
    int buttonCount = 13;
    float angleStep = Mathf.PI*2.0f / buttonCount;
    Vector2 circleCenter = new Vector2(Screen.width/2,Screen.height/2);
    // Set the circle radius
    float radius = 150;
    for (int i = 0; i < buttonCount; i++)
    {
        Rect R = new Rect(0,0,40,20); // adjust the size
        R.x = circleCenter.x + Mathf.Cos(angleStep*i)*radius - R.width/2;
        R.y = circleCenter.y + Mathf.Sin(angleStep*i)*radius - R.height/2;
        if (GUI.Button(R,"but:"+i))
        {
            // do something
        }
    }
}

This will draw 13 (or any other number) buttons in a circular shape.

ps: if you replace the two "angleStep*i" lines with "angleStep*i + Time.time" the buttons will rotate x)