C/Fe. The periodic table of elements codes for Carbon, and Iron. Isaac Asimov first used the combination in his book *The Caves of Steel*:
"See fee? What's that?"
"Just the chemical symbols for the elements carbon and iron, Elijah. Carbon is the basis of human life and iron of robot life. It becomes easy to speak of C/Fe when you wish to express a culture that combines the best of the two on an equal but parallel basis."
"See fee. Do you write it with a hyphen? Or how?"
"No, Elijah. A diagonal line between the two is the accepted way. It symbolizes neither one nor the other, but a mixture of the two, without priority."
The concept is humans and robots working side by side. An old friend of mine back in 1977 coined the phrase "men and machines working together". As far as I know, he never read *The Caves of Steel*.
I would have loved to know Isaac Asimov personally. I could have talked robots with him for hours, I think.