In this chapter the details of implementation of gene expression programming were thoroughly explained, giving other researchers the possibility of implementing it themselves. Furthermore, this new algorithm was summarily compared to genetic algorithms and genetic programming in order to bring into focus the fundamental differences between the three techniques and, consequently, enable readers to appreciate the advantages a full-fledged genotype/phenotype system brings into evolutionary computation. In addition, the classification task solved in this work clearly demonstrates the modeling prowess of this new technique: the compact computer programs evolved by gene expression programming in its native Karva code can be immediately used to generate highly sophisticated computer programs in virtually any programming language through the use of grammars as is already done in commercially available software.