The operating system — the brain between hardware and user
What a control system does, and why you should know its structure
An operating system (control system) is the programme that starts when the machine is turned on and controls everything else. It distributes the machine's resources — processor memory storage and devices — between the programmes running and gives the user and programmes a common predictable basis to work on. Without an operating system each programme would have to talk directly to the hardware itself.
§The core and the user space
The heart of an operating system is called the kernel. It runs with full permissions and has direct access to hardware. Ordinary programs run in user space with fewer permissions and must ask the kernel to perform sensitive operations through system calls. This separation protects the system: a program that crashes or misbehaves cannot easily take the rest of the machine down with it.
§Processes and memory
A running programme is called a process. The control system switches many times a second between processes so it looks like everything is running simultaneously. Each process is allocated a piece of memory it must not write beyond. When memory becomes tight parts can be temporarily moved to storage. If you understand the difference between a process that uses a lot of processor time and one that waits for storage or network you can far better identify what makes a machine slow.
§File system and permissions
The file system organizes data in folders and files and keeps track of where they physically lie on the storage. Each file and folder has permissions that determine who may read, write and run them. Permissions are a cornerstone of security: a user should only be able to reach what the task requires.
- 01Core: runs with full rights and controls the hardware
- 02Process: a running program with its own allocated memory area
- 03File system: organizes data in folders and files
- 04Rights: controls who may read, write and drive
- 05Driver: translates between operating system and a specific device
§Why it matters in operation
When a machine is slow, hangs, or runs out of space, the answer almost always lies in the operating system: a process using too much, memory that's filled up, storage that's filling up, or a faulty driver. If you know where the operating system displays this information, you can target the cause instead of guessing.
“You don't need to know every control system by heart. But if you understand processes, memory, storage and permissions, you can find your way in them all.”
— Professional basic rule in system administration.