2.1.5

Interrupts

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Interrupts

Interrupts are an essential part of modern computer systems that tell the CPU when something needs attention.

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Interrupts

  • An interrupt is a signal from a piece of software or hardware that tells the CPU that it needs some attention.
  • Interrupts are an efficient way of telling a computer when a job needs to be completed.
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Hardware interrupts

  • Hardware interrupts can occur when an input or output operation completes.
  • Hardware interrupts can also involve errors, like when a printer runs out of paper.
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Software interrupts

  • Software interrupts come from pieces of software that need to terminate or request services from the OS to complete a task.
  • For example, opening a document.
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Alternatives to interrupts

  • One alternative to using interrupts is polling.
  • Polling is when the CPU polls (asks) every piece of software and hardware if it needs anything doing.
  • This would be a very inefficient process.

Interrupt Service Routine (ISR)

An interrupt service routine is a set of instructions that need to be done as part of an interrupt.

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ISR

  • An interrupt service routine is a set of instructions that need to be done as part of an interrupt.
  • When an interrupt service routine has been completed, the CPU will go back to the set of instructions it was doing before.
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Process

  • As an interrupt arrives at the CPU it comes with a flag to indicate the priority of the interrupt.
  • This interrupt could be higher importance than the set of instructions it is currently working.
  • The interrupt pushes the current instruction and all the contents of the registers in the CPU to a stack.
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Process cont.

  • The CPU will then complete the interrupt service routine and then load the registers back in from the stack and continue where it left off.
  • At the end of each fetch, decode, execute cycle, the CPU checks for interrupts and their priorities before continuing on.

Jump to other topics

1Components of a Computer

1.1Structure & Function of the Processor

1.1.1Structure of the CPU

1.1.2Fetch, Decode, Execute Cycle

1.1.3Factors Affecting CPU Performance

1.1.4CPU Architecture

1.2Types of Processors

1.2.1CISC & RISC

1.2.2Multicore & Parallel Cores

1.3Input, Output & Storage

1.3.1Computer Systems

1.3.2Magnetic Storage

1.3.3Optical Storage

1.3.4Types of Optical Storage

1.3.5Types of Memory

1.3.6Flash Memory

1.3.7Virtual Memory

2Software & Software Development

2.1Systems Software

2.1.1Operating Systems

2.1.2Managing Memory

2.1.3Paging, Segmentation & Virtual Memory

2.1.4Device Management & Drivers

2.1.5Interrupts

2.1.6Scheduling

2.1.7Types of Operating System

2.2Applications Generation

2.2.1Applications Software & Utilities

2.2.2Encryption & Defragmentation

2.2.3Data Compression & Backup

2.2.4Open Source vs Proprietary Software

2.2.5Translators

2.2.6Compiling a Program

2.2.7Linkers, Loaders & Libraries

2.3Software Development

2.3.1Algorithmic Thinking

2.3.2Waterfall Lifecycle

2.3.3Agile Methodology

2.3.4Extreme Programming

2.3.5Spiral Methodology

2.3.6Rapid Application Development

2.4Types of Programming Language

2.4.1Types of Programming Languages

2.4.2Programming Paradigms

2.4.3Assembly & Machine Code

2.4.4Modes of Addressing Memory

2.4.5Object-Oriented Languages

2.4.6Encapsulation & Polymorphism

3Exchanging Data

3.1Compression, Encryption & Hashing

3.1.1Compression

3.1.2Encryption

3.2Databases

3.2.1Databases

3.2.2Managing Databases

3.2.3SQL

3.2.4Principles of Data Storage

3.3Networks

3.3.1Networks Introduction

3.3.2Types of Networks

3.3.3Network Protocols

3.3.4The Internet

3.3.5DNS & Web Hosting

3.3.6Layers

3.3.7Packet Switching

3.3.8Network Hardware

3.3.9Firewalls

3.3.10Proxies

3.3.11Client-Server Model

3.3.12Peer-to-Peer Model

3.4Web Technologies

3.4.1HTML

3.4.2CSS & JavaScript

3.4.3Search Engine Indexing

3.4.4Server & Client-Side Processing

4Data Types, Data Structures & Algorithms

4.1Data Types

4.1.1Data Types

4.1.2Arrays & Strings

4.1.3Representing Numbers

4.1.4Binary Arithmetic

4.1.5Hexadecimal

4.1.6Converting Binary Numbers

4.1.7Floating Points in Binary

4.1.8Floating Point Arithmetic

4.1.9Bitwise Manipulation

4.1.10Character Sets

4.2Data Structures

4.2.1Arrays, Linked Lists & Queues

4.2.2Graphs, Hash Tables & Stacks

4.2.3Trees

4.3Boolean Algebra

4.3.1Computational Logic

4.3.2Boolean Logic

4.3.3Karnaugh Maps

4.3.4Boolean Identities

4.3.5Flip Flops & Adder Circuits

5Legal, Moral, Cultural & Ethical Issues

5.1Computing Related Legislation

5.1.1Data Protection Act (1998)

5.1.2Computer Misuse Act (1990)

5.1.3Copyright Designs and Patents Act (1988)

5.1.4Regulation of Investigatory Powers Act (2000)

5.2Moral & Ethical Issues

5.2.1Online Activity Tracking

5.2.2Censorship

5.2.3Cultural Issues

5.2.4Environmental Issues

5.2.5Layout, Colour Paradigms & Character Sets

6Elements of Computational Thinking

6.1Thinking Abstractly

6.1.1Abstraction

6.2Thinking Procedurally

6.2.1Decomposition

6.3Thinking Logically

6.3.1Pseudocode & Flow Diagrams

7Problem Solving & Programming

7.1Programming Techniques

7.1.1Programming Fundamentals

7.1.2Modularity

7.2Programming Construction

7.2.1Integrated Development Environments

7.2.2Testing

8Algorithms

8.1Algorithms

8.1.1Interpreting, Correcting & Completing Algorithm

8.1.2Sort Algorithms

8.1.3Insertion & Merge Sort

8.1.4Search Algorithms

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Device Management & Drivers

Scheduling