search for discretization features which is the process of converting real features to nominal features.
this is a nice review about Discretization Techniques: http://www.math.upatras.gr/~esdlab/oldEsdlab/en/members/kotsiantis/discretization%20survey%20kotsiantis.pdf
Yes, 'Real' attribute is a continuous attribute, as opposed to a discrete attribute-- which may be binary (0 or 1), nominal (e.g. red, blue, green), or ordinal (e.g. high, medium, low).
There are various ways to discretize a real attribute into suitable number of categories, but I think that is best done depending on some Class attribute (in case the problem is a classification problem), or a target variable (in a general machine learning problem). This is generally called "Supervised Learning."
The task of discretizing an attribute on an "Unsupervised" basis is a lot more difficult.
A very popular paper on this is by Liu, Hussain, Tan and Dash.
Thanks a lot for your answer sir Partha. could you support me with paper discussing the fuzzy discretizatio , i think it's appropriate for the DNA microarray data which i'm working on