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This paper describes all of the hardware and software interactions and operations for the Space Technology 5 (ST-5) single-board flight computer. This computer, together with the software that runs on it, does much more than just command and data handling (C and DH), but it is called the C and DH subsystem. In order to put the C and DH design in perspective, the paper starts with an overview of the ST-5 mission and a review of the spacecraft technologies that will be flight validated by ST-5. Following that, there is an introduction to the spacecraft itself, with a discussion of the spacecraft's mechanical design and two-slot "card cage" that houses the C and DH electronics circuit card (or board) and the power system electronics circuit card (or board). A summary of the key C and DH requirements leads into a more in-depth presentation of all the C and DH interfaces and functions, including how the electronics hardware and flight software operations are partitioned in order to meet the overall requirements for ST-5. The details of the C and DH board design are given in terms of the processor, memory, gate arrays, power conditioning, physical dimensions and layout. A description of the development, integration and test flow precedes the paper's conclusion.