A: Some lines as follows appear in the output file:

Found probable prime factor of 38 digits: 15697920117275073486338469567634384633

Probable prime cofactor 248224208600891230638840397209907041348178075109876163768459663055209916421778767469609238164044706325366885940218654867062058537 has 129 digits

**Q: How to use ecm.exe as batch file under Windows?**

A: See the
ecmloop.bat file from Warut Roonguthai

**Q: The value of B1 in the output file cunningham.out is always 0.
What happens?**

A: Please check your command looks like "`ecm 3000000`".
Check "`ecm -v`" for more information about the command line.

**Q: What do the lines "recognized factor of 2^631+1, using special base-2 division" mean?**

A: They mean the program has detected the input number if a divisor of a power
of two plus or minus one, and is using a faster division. This does not mean
a new factor was found.

**Q: Can I change the recommended value B1=3000000?**

A: Yes: a smaller (resp. greater) value will take less time per curve and
will have less (resp. more) chance of finding a factor. However this value of
B1=3000000 is optimal for the expected size of new factors (about 40 digits).
See the
table of optimal B1 wrt factor size.

**Q: Do I loose all results if I restart the program?**

A: No, you only loose the computations done in the current curve.