The "t" (test) instruction with the sign-bit option and the "Transfer Control" button are mentioned in the post as well (see operations). On the LGP-30 this wou

The "t" (test) instruction with the sign-bit option and the "Transfer Control" button are mentioned in the post as well (see operations). On the LGP-30 this would have been the only means of manipulating the control flow from the console in a sensible manner. (I didn't have a look into the RPC-4000 yet, so I really don't know, if there had been additional options.) So the way to implement an option would have been to have a zero or positive value in the accumulator and then have a test instruction with the sign-bit set. If the "Transfer Control" button was deployed, we would take the branch (unconditionally), if not, we'd fall through to the next instruction, since the condition 'AC negative' was not met.