How is the Linux operating system structured — processes, threads, memory?

Linux is a multitasking operating system with processes and threads managed by the kernel.

Processes are isolated instances of programs, each with its own address space, file descriptors, and resources. A process is created through the system call fork() or clone(), which creates a copy of the parent process.

Threads are execution units within a process that share the process's memory and resources but have their own stack and registers. In Linux, threads are implemented as lightweight processes (LWP) using clone() with different flags.

Memory in Linux is organized through virtual memory divided into pages. Each process has its own virtual address space, which the kernel maps to physical memory. There are several memory segments: code, data, stack, heap. Memory management includes swapping, caching, and access protection.

Example: When a program is launched, a process with virtual memory is created, and within the process, threads can be created for parallel execution, which share the process's memory.