I get some junk forwarded mails once in a while. Some of them I delete it just by looking at the subject line but some of them I open it in curiosity. And most of the time more than the content what annoys me more is the huge To address list which sometimes would be bigger than the mail itself. If you want to send a mail to lot of people, address everyone in Blind Carbon Copy (BCC) unless and otherwise you specifically want to address in To or Carbon Copy (CC). Here are few advantages I can think of using a BCC when sending a mail to numerous recipients.

1. As the name suggests the recipients do not know who else recieved the mail and that helps in maintaining privacy of everyone’s ID.
2. It is a good anti-spam protection mechanism because of point 1 and could prevent phishers from getting the mail id’s in bulk.
3. If you don’t want the recipients to reply back to everyone then you can use BCC and include any ID in the TO of CC that the recipients can reply to (when selecting reply all).
4. The address section of the mail looks neat as the recipient would see only his ID in the BCC text box.

If you are a night sky watcher and want to know about the stars and their positions this flash based planetarium could bring the sky down to your computer. It shows the current position of stars and also the position on any day. Mouse over on a star to know the name and its magnitude.

Happy Weekend!

One of the good design principles is to program to an interface. What does programming to an interface mean? An easy way to explain this is to think of the domain model of a system to be defined in terms of (Java) interfaces. These definitions are like vocabulary of the system as these do not contain implementation but just declarations. The system using the domain works against the interface and does not know what is going to be the implementation until run time. A factory, a broker or a container could actually help get an implementation during runtime. The key advantage is the layer that uses the interface is loosely coupled with implementation and there could be several implementations of the domain model that suits specific situations/needs. What other advantages does programming to the interface bring? And why not an abstract class instead of interface? This, year old interview “A Conversation with Erich Gamma” by Bill Venners best answers these questions.

Those number1.number2.number3.number4 way of accessing a machine or URL or when you ping a site what you see, yeah you are right the IP address, ever wondered why that format and what it signifies and how does it work? The number is decimal representation of each byte in the 4 bytes (that is why the range of IP address can be in the combination of 0.0.0.0 to 255.255.255.255 ) that is used to store a machine address. In that case do you think we can connect to a machine using a complete decimal representation of the 4 bytes? Why don’t we try it? Let’s try to access google.com using a decimal representation.  First get the IP address of google.com by pinging it in your shell. The IP I got was from the Google server in India ( google.co.in) which is 64.233.189.104. Let’s take each number here and convert it into binary.  Remember to pad zeros in the left if the number does not translate to 8 bits. Use scientific calculator mode in XP and it will help conversion easy. So here is the binary representation of each number.

64  - 01000000
233 - 11101001
189 - 10111101
104 - 01101000

Now combine the binary above together as 32 bits which gives 1000000111010011011110101101000. Now translate this back to decimal which is 1089060200.  Now to verify that if this number will take you to Google why don’t you click this link http://1089060200. I got the Google India search page! So each of that byte has significance and can determine the IP class. Learn more about “The IP Address and Classes“.

When I was in my college days learning UNIX, me and my friends used to play around with commands that display back a funny message. The command is wrong and is like a question but UNIX responds back with an error message that looks like an answer to that question and it is funny. I just stumbled upon this list again, though most of these do not work in the current *nix environments.

Sometimes wonder why some sites you are trying to access seems to be very slow even though you have a high speed internet connection? If you didn’t know that the amount of distance from where you are in to the machine you connect to did not have an effect on the time it takes for the page to load then you need to know something about the network latency.  More often we talk about bandwidth but not hear anything about latency. The network latency is the time it takes from the moment the destination receives the request until the response arrives back to your machine. More detailed explanation on latency from this little old yet very informative article “It’s the Latency, Stupid“.