system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why is it almost impossible to “decompile” executable (.exe) files to reveal the package contents?
gpt
Executable files are made of machine code, which is translated (assembled) from a family of programming languages called assembly. It is (usually) possible to reverse the process (disassembling) and get the same assembly code back, because the assembling process is (usually) lossless. Assembly code and machine code are very simple (relatively speaking) - there are no variables beyond a set of registers that are used and reused throughout the program for various purposes, and access to main memory.

Most programs are not written in assembly code. Instead, they are written in higher-level languages that have fancy things like variables, flow control, loops, comments, and multiple files. When these programs are compiled to assembly, a lot of information in the original program is lost, like variable names, because assembly doesn't have a way of representing that information. If you want to reverse the process, you need to output that lost information elsewhere (like a file of debugging information that maps generated assembly code to the original source code), or deal with a translation with generated variable names and a very simple representation of the program logic.

It's like trying to translate a sentence through a series of languages and back to the original - information is going to get lost because of differences between the languages. However, a decompiled program should still have the same function as the compiled executable, since programming languages aren't subject to as many nuances as human languages.