Clarification on Alphanumeric Password and Character Set

Hello,

Could you please let us know what does a Alphanumeric Password and Character Sets means?
We have tested Alphanumeric Password & Character set on few devices and observed different behavior on every device.

What exactly should happen when character sets of length 1,2,3,4 along with Alphanumeric password and Min password length of 'n' characters is applied from Exchange management console?
Note: Simple Password is not allowed

Please give few possible passwords for the below mentioned scenarios

Character Set   Min LengthPossible Passwords
14????
24????
34????
44????

15?????
25?????
35?????
45?????

Thanks,

Deepu Pasula