67/97 card read bug on the HP41

[hth]

Just a follow up on this, I have still no idea what the 67/97 card reader bug is.

A buffer must have the last register as non-zero. This is because registers are allocated for programs by taking the next zero register after the permanent .END. If the last register of the last buffer is zero, it could be consumed for program memory. The routine that scans for the number of free registers available also checks the number of zero registers below .END.

It is a pity we do not have a comprehensive list of known bugs.