REFACTORING:

>From "Refactoring: Improving the Design of Existing Code," , Martin Fowler
, Addison-Wesley, 1999, p. xvi 


What Is Refactoring?
Refactoring is the process of changing a software system in such a way
that it does not alter the external behavior of the code yet improves its
internal structure. It is a disciplined way to clean up code that
minimizes the chances of introducing bugs. In essence when you refactor
you are improving the design of the code after it has been written. 

"Improving the design after it has been written." That's an odd turn of
phrase. In our current understanding of software development we believe
that we design and then we code. A good design comes first, and the coding
comes second. Over time the code will be modified, and the integrity of
the system, its structure according to that design, gradually fades. The
code slowly sinks from engineering to hacking. 

Refactoring is the opposite of this practice. With refactoring you can
take a bad design, chaos even, and rework it into well-designed code. Each
step is simple, even simplistic. You move a field from one class to
another, pull some code out of a method to make into its own method, and
push some code up or down a hierarchy. Yet the cumulative effect of these
small changes can radically improve the design. It is the exact reverse of
the normal notion of software decay. 

With refactoring you find the balance of work changes. You find that
design, rather than occurring all up front, occurs continuously during
development. You learn from building the system how to improve the
design. The resulting interaction leads to a program with a design that
stays good as development continues 

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There are excellent online resources on Refactoring. So I will simply
quote them here. ;) (reuse) ;)

http://www.refactoring.com/ - The official web site of refactoring. It
contains a summary of the book, and a concise writeup on the refactoprings
given in the book:

http://www.refactoring.com/catalog/index.html for the catalog of
refactorings.

Some refactoring browsers are available, or in the making. You will find
links to them. Refactoring makes a very good project for people interested
in programming languages/ compilers.

Some other links are:

http://www.volantec.biz/refactoring.htm
http://www.cs.unc.edu/~stotts/COMP204/refactor/