Modification of existing executable code and/or running processes is a rather broad theme, which is very difficult to fit into a single chapter as it may itself deserve a separate book. It is, however, much more relevant to programming techniques, and operating systems in general, while we were trying to concentrate on the Assembly language.
This chapter hardly covers the tip of the iceberg called modification of binary code (known as patching). The purpose was to demonstrate how easy and interesting the process may be, rather then covering each and every method in much detail. We have, however, acquired a general indication of where to go to when it comes to modification of code that cannot be simply rebuilt.
The method of code analysis was covered very superficially just to provide you with the general idea, just as the most part of the process of patching an application...