Sorry for the wrong "subject line" in the message posted a moment ago.
It ment to be "Sophisticated calculators". This one is about Mac.
No more troubles with MAC OS 8.1. Freezings (at OS level) were probably
due to too many active extensions, as suggested in several messages. In
particular network-related extensions are now deactivated because my
computer is not connected to a network.
Before I typically had one or two freezes each day. And now not a single
freeze in three days. I hope it will stay this way. Thanks to all who
responded.
Ludwik Kowalski