> a new library for Apple platforms that provides idiomatic interfaces to system calls and low-level currency types

In other words, it's a set of native, type-safe Swift APIs that wrap the usual C system calls.

> System pervasively uses raw representable structs and option sets. These strong types help catch mistakes at compile time and are trivial to convert to and from the weaker C types.

> Errors are thrown using the standard language mechanism and cannot be missed. Further, all system calls interruptible by a signal take a defaulted-true retryOnInterrupt argument, causing them to retry on failure. When combined, these two changes dramatically simplify error and signal handling.

> FilePath is a managed, null-terminated bag-of-bytes that conforms to ExpressibleByStringLiteral — far safer to work with than a UnsafePointer<CChar> [Swift's spelling of `char *`].