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Kernels, sometimes called the “system core,” are the bridge between software and hardware. It controls CPU usage, processes, and hardware (input/output, abbreviated I/O, also called stdin/stdout in programming contexts). For example: The keyboard sends a key to the device (Input) –> Keyboard driver –> Kernel processes –> Input event –> The kernel places this in the output, located at /dev/stdout (a symbolic link to /proc/self/fd/1). —
A complete operating system is not only the kernel. The kernel provides interfaces such as /dev, /proc, and /sys, which expose hardware and system information to user space. User space includes applications, libraries, and binaries typically located in directories like /usr and /opt. Together, kernel and user space form a complete operating system. —
Linux distributions are complete operating systems built on top of the Linux kernel. For beginners, we can recommend…: