The CoCo SDC is a floppy disk emulator for the Tandy Color Computer (CoCo), designed by Darren Atkinson. It allows users to store CoCo disk images on an SD card and use them on their CoCo via the on-board SDC-DOS. This provides a modern storage solution for the CoCo, eliminating the need for older, potentially unreliable floppy drives or cassette recorders.