1. A method of modifying a classification scheme stored by a processing system for classifying hand-written characters to thereby make the classification scheme user dependent, the processing system storing the classification scheme to include a plurality of classes and user dependent weighted allographs, each class representing a respective letter and containing one or more of the allographs, each allograph including an associated weighting and representing a respective style of a respective letter and containing one or more prototypes, each prototype representing a variation in the respective allograph and being represented as a prototype vector, each prototype vector being formed from a number of values, each value quantifying a respective feature of the respective prototype vector, the method including the steps of: obtaining at least one hand-written character at an input of the processing system; determining, in the processing system, a selection value based on the similarity of the obtained character and a respective prototype vector of the stored classification scheme by: determining a feature vector representing the character, the feature vector being formed from a number of values, each value quantifying a respective feature of the character; and determining a distance value representing the distance between the determined feature vector and said respective prototype vector; selecting, in the processing system, a respective one of the prototype vectors of the stored classification scheme in accordance with the determined selection values; selecting, in the processing system, a class of the stored classification scheme in accordance with the selected prototype representing the character to thereby determine the letter represented by the character; selecting, in the processing system, one of the stored user dependent weighted allographs in accordance with the weightings and in accordance with said selected prototype vector representing the character; and modifying, in the processing system, one or more of the allographs in the respective class in accordance with the selection by modifying the weighting of one or more of the allographs; storing a modified classification scheme in the processing system which includes said modified allographs.