Monaco is a monospaced sans-serif typeface designed by Susan Kare, Kris Holmes, and Charles Bigelow. It ships with macOS and has been present in all releases of Macintosh system software since the first Macintosh in 1984. Characters are distinct, and it is difficult to confuse 0 and O, or 1, |, I and l. A unique feature of the font is the high curvature of its parentheses as well as the width of its square brackets, the result of these being that an empty pair of parentheses or square brackets will strongly resemble a circle or square, respectively.