A method of using a computer program that accesses legacy program code can include distinguishing between non-legacy program code of the computer program and legacy program code of the computer program, separating the computer program into at least a first logical unit including non-legacy program code and at least a second logical unit including legacy program code, and including interface code within the first logical unit. The interface code can be non-legacy program code that communicates with the second logical unit. The first logical unit and the second logical unit can be output.