Unlock Huawei modem

I've read many places where people r demanding money for unlocking modem.They write Email and Bank A/C details for money transfer, its funny.For only few digits they r charging money so I've decided to disclose all the science behind this.
Commonly the unlock code depends upon the IMEI no. and that IMEI no. uniquely identify each modem.
To calculate unlock code u can use online calculator from given url http://a-zgsm.com/huawei.php
or if u want to get own calculator, u can download from this link http://www.mediafire.com/?dtm5kwjmomx.
This is a universal calculator that can unlock Huawei,Nokia,Zte,Nec and others.
If u feel any problem u can write here.