Carbon-based nonvolatile resistive memories are an emerging technology. Switching endurance remains a challenge in carbon memories based on tetrahedral amorphous carbon (ta-C). One way to counter this is by oxygenation to increase the repeatability of reversible switching. Here, we overview the current status of carbon memories. We then present a comparative study of oxygen-free and oxygenated carbon-based memory devices, combining experiments and molecular dynamics (MD) simulations.