Describe the primary purpose of an operating system, and then discuss at least three features that modern operating systems provide.

The primary purpose of an operating system (OS) is to manage the computer hardware and software resources. It acts as an intermediary between the user and the computer hardware and controls the execution of all kinds of programs.

Here are three features that modern operating systems provide:

1. Process Management: The OS manages all the processes running on a system. It allocates resources, schedules execution time, and handles process communication and synchronization.

2. Memory Management: The OS is responsible for managing the computer's memory. It keeps track of each byte in a system's memory and which processes are using which memory.

3. File System Management: The OS provides a way for programs and users to create, write, read, and delete files. It also manages file permissions and file storage.

These are just a few of the many features and functions that an operating system provides. Other features include device management, security, and user interface, among others.