Final answer:
The programming language for creating apps for Apple iOS devices with touchscreen interfaces mentioned in Chapter 13 is Swift.
Step-by-step explanation:
The programming language introduced in Chapter 13 that uses a graphical user interface and special code for touchscreen interfaces to create apps for Apple iOS devices is called Swift. Swift is known for its modern features that make code easier to read and write, while also providing the frameworks necessary for developing iOS applications with interactive user interfaces. Additionally, Swift integrates well with Apple's development tools such as Xcode, which provides a robust environment for designing and testing iOS apps.