SCC.131 Digital Systems - Operating Systems

Flashcards for reviewing Operating Systems concepts, including OS definition, kernel functions, processes, threads, and scheduling algorithms.

What is an Operating System (OS)?

A software program that manages all the hardware and software on a computer, acting as the bridge between the user and the computer's physical components.

What are the main tasks of an Operating System?

File management, Memory management, Process management, Input/Output handling, Security & Access Control, Multitasking & Scheduling.

What is the purpose of the Operating System?

Manages and allocates resources, controls the execution of user programs and operations of I/O devices.

What is the Kernel?

The core of a computer's operating system (OS) that acts as an interface between the hardware and the rest of the OS, running at all times.

What are the two common designs of kernels?

Monolithic kernels and Micro-kernels

What is the difference between user-mode and kernel-mode?

Kernel-mode has unrestricted access to the machine, while user-mode has limited access.

What are Protection Rings?

Domains that are an architecture used to regulate access to system resources and prevent unauthorized actions by providing different privilege levels.

What is the purpose of Protection Rings?

Security, Stability, Efficiency, and Improving fault tolerance.

What happens when User-mode code attempts direct hardware access?

The processor will detect the unauthorized operation and generate a trap or fault, allowing the operating system’s kernel to interfere.

In the context of operating systems, what is a process?

A program running on the machine, managed by the OS, with tracked code, memory, system resources, security permissions, and hardware context.

What is a thread and how does it relate to a process?

A thread shares the same resources as its parent process but executes independently, allowing for lightweight and fast context switching, memory sharing, and parallel execution.

What is Scheduling in the context of operating systems?

The method by which the OS decides which processes or threads will be assigned to the CPU for execution, ensuring efficient CPU utilization and fair process execution.

What are the two types of multitasking?

Pre-emptive Multitasking and Cooperative Multitasking

Name four scheduling algorithms.

First-Come, First-Served (FCFS), Shortest Job Next (SJN or SJF), Round Robin (RR), and Priority Scheduling.

What are the three types of scheduling?

Long-Term Scheduling (Job Scheduling), Short-Term Scheduling (CPU Scheduling), and Medium-Term Scheduling

Why is Scheduling Important?

Ensures fairness, Maximises CPU utilisation, Minimises response time, and Balances system load.