Today's post is about what you should know about Iostreams. In particular, I write about formatted and unformatted In- and Output.

When you interact with the outside world, the iostream library is the way to go in C++. As always you have to keep a few rules in mind. Let me show, which rules.

The C++ core guidelines use the term string as a sequence of characters. Consequently, the guidelines are about  C-strings, C++-strings, the C++17 std::string_view's, and std::byte's. 

When you access an element outside a container of the STL, the result is not so promising. You effect may be an error or undefined behaviour. Undefined behaviour means all bets are open.

Modern C++ has eight associative containers, but your special friends should be std::map and std::unordered_map. Why? Let me explain it in this post.

In 99 % of your use-cases for a sequential container, you are totally fine with a std::array or a std::vector. What? If you don't believe me, read this post.

The rules to the C++ standard library are mainly about containers, strings, and iostreams.

 My last post gave you the introduction to modules in C++20. This post shows, how to use existing modules.

Modules is one of the five prominent features of C++20. Modules will overcome the restrictions of header files. They promise a lot. For example, the separation of header and source files becomes as obsolete as the preprocessor. In the end, we will also have faster build times and an easier way to build packages.

Today, I complete the rules of the C++ core guidelines to source files. They are about header files and namespaces.