HP -65 Owner's Handbook Manual page 83

Overflow
If a computation develops a magnitude that exceeds the capacity
(>10%) of a register, the result is set to all 9's (with appropriate
sign), the largest magnitude expressable in a register and the
program stops, if running.
Temperature Range
The operating temperature range for the HP-65, including charg-
ing, is 10° to 40°C (50° to 104°F).