As spc476 answered 1), I'll just expand on 2). Emacs would be an example of the link approach. It includes an editor and an email program, which are composed i

As spc476 answered 1), I'll just expand on 2). Emacs would be an example of the link approach. It includes an editor and an email program, which are composed into a single program/image. In contrast, the Unix functionality (vim,sendmail) is split into separate programs. What is the difference between a function call and a program invocation? In both cases we have a name and maybe some arguments. In both cases the computer executes some code bound to that name parameterized with our arguments. The difference is primarily, how expensive is the name resolution. A shell command requires inspecting $PATH, looking through directories, fork/exec another program, which is a lot syscalls. A function call in the best case has been compiled to a "call" instruction, whose cost depends on the branch prediction. Of course, there are various levels in between (dynamically linked libraries, plugins, shell builtins, etc). There are more complex composition methods like SAAS or cloud computing. There are more efficient methods (inlining optimization). Semantically, it is interesting when a name is resolved. Compiled languages (C,Go) usually do this statically at compile time, where C is even more restrictive as it only looks above in the code. Dynamic languages (Python,Ruby) do it at runtime. In general, early binding is usually good for performance, while late binding is better for flexibility.