A2 OCR ICT: Chapter 2 - Operating Systems

Notes from OCR A2 ICT Textbook.

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Operating Systems: Introduction

Types of Operating Systems:

> Single-User

> Multi-User

> Multi-Tasking

> Interactive

> Real-Time

> Batch Processing

> Distributed Processing

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Operating Systems: Single-User

> In a Single-user Operating System(OS) only one person can use the system at a time, however there can be multiple accounts on the system. In order for someone else to use the system, the current user must first log off and the new user log in.

> In a Single-User OS multi-tasking is possible as the processor is dedicated to that single user.

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Operating Systems: Multi-User

> A Multi-User OS allows multi users to log in simultaneously.

> This type of OS is usually provided by a network.

> The most common form of this system is a Single-User Operating system, connected to a server that has a Multi-User OS, via a network.

> The system manages all the users requests and makes sure that the requests do not interfer with each other.

> With this system several computers can share peripherals, such as printers.

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Operating Systems: Multi-Tasking

> A Multi-Tasking OS can carry out multi tasks at a time.

> EG. Using the internet and a spreadsheet

> Most types of the system do not actually do multi-tasks at a time, they complete part of one task, then part of another. repeating the process until all the tasks are complete. However the system does this so quick it appears that it is doing both at the same time.

> In order for a system to do multi tasks simultaneously multi processors are required.

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Operating Systems: Interactive

> An interactive OS is where there is direct user interaction while a program is running

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Operating Systems: Real-Time

> A Real-Time OS is commonly used for embedded applications.

> Embedded applications are systems within a device/application.

> EG. An Engine management system in a car.

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Operating Systems: Batch Processing

> Batch OS is given tasks to complete/run without any intervention from the user.

> The tasks are collected, stored and run when there is less demand on the system.

> Alternatively, the system can be set so that the tasks are run just before the results are


> EG. Payroll calculations just before the end of the month.

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Operating Systems: Distributed Processing

> A distributed processing system involves multi computers connected together.

> Each computer in this network completes part of the processing, and at the end the results are combined to meet the requirements of the user.

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