Why a "vlan.dat" file for an IOS switch?

It looks to me the "vlan.dat" design will stay a long life on IOS switches.

How to remove VTP domain string: 2 reloads

To restore a IOS switch to a "whole new" state, it is necessary to clear even the "VTP domain" string to null. I thought at first just remove "vlan.dat" followed by a reload would do it, but now I found that I was NOT quite correct!

Binary and Decimal number conversion practice

 153 =  1    0    0    1    1    0    0    1 
       ---  ---  ---  ---  ---  ---  ---  ---  
       128   64   32   16   8    4    2    1 

       2^7  2^6  2^5  2^4  2^3  2^2  2^1  2^0 

We must be skillful enough about conversions between binary and decimal number when we are learning IP address and subnet mask writing. It would be especially helpful if we have a self-practice environment.