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A #ComputingHistory question that came up today: what is the origin of | (the vertical stroke) as bitwise OR in PL/I, and thence to the C family of languages?

I haven't been able to trace it further back, and interestingly in logic it was the "Sheffer Stroke", NAND (although Wikipedia claims that Sheffer actually used it for NOR instead?) There does not seem to be a logic or typesetting convention that birthed |.

I don't know enough about early IBM keyboards to know what other characters might be available.

The choice of & for AND instead of ^ -- it's right there! -- is similarly unclear.