OCR Computer Science A Level - Systems Software

A series of flashcards covering key concepts and definitions related to operating systems and systems software in the OCR Computer Science A Level.

Operating System

A collection of programs that provides an interface between the user and computer.

Memory Management

The process of sharing computer memory fairly between multiple programs and applications.

Paging

A memory management scheme that eliminates the need for contiguous allocation of physical memory and eliminates the issues of fitting varying sized memory chunks onto the backing store.

Segmentation

Dividing memory into logical segments of varying sizes, representing the structure and logical flow of a program.

Virtual Memory

Uses a portion of the hard drive to extend available RAM by temporarily transferring sections of programs not currently in use.

Interrupts

Signals generated by software or hardware to indicate to the processor that a process needs attention.

Interrupt Service Routine (ISR)

Code that is executed in response to an interrupt.

Scheduling Algorithms

Methods used by the operating system to allocate processing time to jobs.

Round Robin

A scheduling algorithm where each job is given a fixed time slice to execute.

First Come First Served (FCFS)

A scheduling method that processes jobs in the chronological order they arrive.

Multilevel Feedback Queues

Scheduling that uses multiple queues, each with a priority level.

Shortest Job First (SJF)

A scheduling strategy that processes the shortest jobs first to minimize waiting time.

Shortest Remaining Time (SRT)

A scheduling method that prioritizes jobs based on the remaining time needed for completion.

Distributed Operating System

An OS that runs across multiple devices to share the load among processors.

Embedded Operating System

An OS designed for a specific device and limited tasks.

Multi-tasking Operating System

An OS that allows multiple tasks to be executed seemingly simultaneously.

Multi-user Operating System

An OS that enables multiple users to access a single computer system.

Real Time Operating System

An OS designed to guarantee task execution within a specific time frame.

Basic Input Output System (BIOS)

The first program that runs when a computer is turned on, responsible for hardware checks.

Device Drivers

Programs that allow the operating system to interact with hardware devices.

Virtual Machine

A software implementation of a computer system that provides an environment to run other operating systems.

Intermediate Code

Code that is midway between machine code and object code, designed to be architecture independent.