Based on the gene expression programming（GEP） proposed by Feriera

from the viewpoint of methodology of automatic programming

this paper investigates the representation of program for program reuse.① A new gene structure is proposed: head + body +tail

which allows the program with necessary complexity and putting some learning mechanism into the search process.② A new homeotic gene structure is proposed

it not only can call for subroutines easily

but also can automatically perform programming.③ The concept of different homeotic gene

a multi-cellular structure is proposed.It can be used to describe the complex multi-level programs and to implement the complex subroutine calls.④ An estimation of distribution operator for guiding search is proposed.It fuses statistic learning mechanism into the search process to accelerate the convergent process and improve the quality of solutions.Numerical experiments show that the new method of automatic programming is very practical.