Day: April 17, 2001

JavaWorld article on polymorphism

netjeff

“Reveal the magic behind subtype polymorphism” is a decent article on polymorphism.

It talks about the four types of polymorphism: coercion, overloading, parametric, and inclusion (sub-type). Most OO developers are comfortable and familiar with the first two. Since the article is java focused, it can’t really give example of parametric polymorphism (templates in C++), but it still talks about the principals of this type of polymorphism.

The last type for polymorphism, inclusion, s the one that is the least understood. In fact, it’s the one that I always ask about when interviewing an OO programmer.

How much information is there in the world?

netjeff

Maichael Lesk speculates in this 1997 article:

How much information is there in the world? This paper makes various estimates and compares the answers with the estimates of disk and tape sales, and size of all human memory. There may be a few thousand petabytes of information all told; and the production of tape and disk will reach that level by the year 2000. So in only a few years:

  • we will be able save everything — no information will have to be thrown out
  • the typical piece of information will never be looked at by a human being.

Later in the article, he estimates that the average human being can store (remember) around 200 MB of data.