The main purpose of an operating system in a computer is to manage hardware and software resources while providing a user interface for interaction. It acts as an intermediary between users and the computer hardware, facilitating essential functions such as task scheduling, memory management, and device control. Popular operating systems, like Windows, macOS, and Linux, provide various features to improve usability and performance. Additionally, the operating system enables the installation and execution of applications, ensuring that users can efficiently leverage the computer's capabilities for their tasks.