M4 is a general-purpose macro processing language used by programmers for a wide range of tasks. It is often used in conjunction with other programming languages, such as C, to provide a powerful yet easy-to-use preprocessor.
M4 has a simple syntax that is easy to learn, yet it is also very powerful. It can be used to perform a wide range of tasks, such as expanding macros, generating code, or even creating entire programs.
Despite its power, M4 is still a relatively unknown language. This is likely due to the fact that it is not often taught in schools. However, for those who are looking for a powerful yet underutilized language, M4 is definitely worth checking out.