The std libraries define the primitives we have already encountered (array, different sized floats and integers, String, and so on), but also contain a number of other modules. They also define the commonly used macros (such as write! and println!).

For the purposes of this chapter, we will cover only std::io, std::fs, and std::fmt. These deal with input/output, the filesystem, and formatting. The io and fs modules will be dealt with later in this chapter.