There was a novel about this: a programmer was coding a robot, it's silicon brain was a sphere as I recall, and he programmed it by just thinking. But his mind

There was a novel about this: a programmer was coding a robot, it's silicon brain was a sphere as I recall, and he programmed it by just thinking. But his mind wandered and he accidentally hard coded the Declaration of Independence (I think) into the thing. It ended up being the nav computer on a cargo ship with one operator on board. They crash-landed on a habitable planet and the operator worked with the brain to make it a new body form: a horse. They then ran into, of course, people in a medieval state of history. And the duo from space has to figure out how to survive, which involves acquiring useful things from the villagers, while protecting their true identity. The horse turns out to be quite helpful, but has an occasional glitch.