Since I completed portable executable C++ library development, it would be totally wrong not to use it in any more or less serious project. Thus I am going to develop a packer with step-by-step explanations of what I am doing, and C++ library will make our life easier. So, where do we start the development? Maybe, from choosing some free simple compression algorithm. After short search I found such one: LZO. It supports lots of compression modes, and LZO1Z999 is the most effective by compression ratio of all available. Of course, it is not like ZIP, but its performance is close: 550 Kb file was compressed to 174 Kb with zip with maximum compression level, at the same time LZO compressed this file to 185 Kb. However, LZO has much more fast unpacker. It is also base-independent, that means, it can be placed at any virtual address and it will work without any address corrections. This algorithm will be right for us.