Cause of Misattributions Regarding Turing and the Halting Problem

Ascertain whether misunderstanding of Turing’s terminology of "circular" and "circle-free" machines is responsible for the misattributions, in the quotations compiled in Section "Did Turing prove the undecidability of the halting problem?", that credit Turing (1936) with proving the undecidability of the halting problem.

Background

The authors propose that some misattributions might stem from a misunderstanding of Turing’s term "circle-free" as meaning "halts," which would wrongly identify Turing’s circle-free problem with the halting problem. They report observing this misunderstanding among students and online discussions.

They explicitly state that they do not know whether this misunderstanding actually explains the specific misattributions documented earlier in the paper, leaving it as an unresolved question in the historical analysis.