This is a summary of what I’ve found. It is likely to get updated from time to time.
s flags
| s0 | n/a | not used. |
| s1 | SCI | Set for scientific notation, clear for fixed. |
| s2 | auto_enter | A digit will push the current X up the stack. |
| s3 | radians | Set if the DEG-RAD switch is in the RADians position. |
| s5 | power_ok | A value of 0 indicates low power. |
| s9 | dot_pressed | During data entry etc, a “.” has already been pressed. |
| s13 | g_pressed | The blue function key was pressed. |
| s15 | key_down | Set while a key is being pressed. |
Addresses
| 00376 | waitloop |
| 00007 | display |
| 00403 | keypressed |
Other
| f | DSP precision |
| M1 | Memory |
This is part of the HP-21 topic.
It's only fair to share...
