3.1.3

Dictionary Coding

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Dictionary Coding

Dictionary coding is used to store text in a lossless format.

Dictionary coding

Dictionary coding

The coder scans through a body of text.
Each word is replaced by the binary number of the word in a dictionary.
Each time it finds a new word which is not in its dictionary, it will add it to the dictionary and give it a binary number.
The word in the actual text is replaced with the binary number.

Benefits of dictionary coding

Benefits of dictionary coding

Dictionary coding is a type of compression. It takes less bits to store a 2 digit binary number than we can a 10 letter word.
No data is lost, so the coding is lossless.
The encoder may not always build its own dictionary. A pre-existing dictionary may be used to encode the text.

1

Components of a Computer

2

Software & Software Development

2.1

Systems Software

2.1.1Operating Systems 2.1.2Managing Memory 2.1.3Paging 2.1.4Segmentation 2.1.5Device Management & Drivers 2.1.6Interrupts 2.1.7Interrupt Service Routine (ISR)2.1.8Scheduling 2.1.9Types of Scheduling 2.1.10Types of Operating System 2.1.11BIOS 2.1.12Virtual Machines

2.2

Applications Generation

2.2.1Applications Software 2.2.2Utilities 2.2.3Encryption Software 2.2.4Defragmentation Software 2.2.5Data Compression Software 2.2.6Backup Software 2.2.7Open Source Software 2.2.8Proprietary Software 2.2.9Licensing Issues 2.2.10Compilers 2.2.11Interpreters 2.2.12Assemblers 2.2.13Compiling a Program 2.2.14Lexical Analysis 2.2.15Compilation Stages 2.2.16Linkers, Loaders & Libraries

2.3

Software Development

2.3.1Algorithmic Thinking 2.3.2Waterfall Lifecycle 2.3.3Waterfall Lifecycle - Strengths & Weaknesses 2.3.4Agile Methodology 2.3.5Agile Methodology - Strengths & Weaknesses 2.3.6Extreme Programming 2.3.7Extreme Programming - Strengths & Weaknesses 2.3.8Spiral Methodology 2.3.9Spiral Methodology - Strengths & Weaknesses 2.3.10Rapid Application Development 2.3.11RAD - Strengths & Weaknesse

2.4

Types of Programming Language

2.4.1High Level Programming Languages 2.4.2Low Level Programming Languages 2.4.3Programming Paradigms 2.4.4Procedural Programming Languages 2.4.5Assembly 2.4.6Machine Code 2.4.7Modes of Addressing Memory 2.4.8Object-Oriented Languages 2.4.9Classes 2.4.10Objects 2.4.11Encapsulation 2.4.12Polymorphism

3

Exchanging Data

3.1

Compression, Encryption & Hashing

3.1.1Compression 3.1.2Run Length Encoding 3.1.3Dictionary Coding 3.1.4Encryption 3.1.5Symmetric Encyrption 3.1.6Hashing

3.2

Databases

3.2.1Records 3.2.2Databases 3.2.3Relational Databases 3.2.4Entity Relationship Modelling 3.2.5Managing Databases 3.2.6Normalisation 3.2.7SQL 3.2.8Principles of Data Storage 3.2.9Atomicity, Consistency, Isolation & Durability

3.3

Networks

3.4

Web Technologies

3.4.1HTML 3.4.2CSS 3.4.3JavaScript 3.4.4Search Engine Indexing 3.4.5PageRank Algorithm 3.4.6Server & Client-Side Processing

4

Data Types, Data Structures & Algorithms

4.1

Data Types

4.2

Data Structures

4.2.13D Arrays 4.2.2Linked List 4.2.3Queues 4.2.4Graphs 4.2.5Hash Tables 4.2.6Stacks 4.2.7Trees 4.2.8Binary Search Trees

4.3

Boolean Algebra

4.3.1Binary Systems 4.3.2Logic Circuits 4.3.3Boolean Operators 4.3.4Evaluating Expressions 4.3.5Boolean Logic 4.3.6Karnaugh Maps 4.3.7Boolean Identities 4.3.8Boolean Rules 4.3.9Flip Flops 4.3.10Adder Circuits

5

Legal, Moral, Cultural & Ethical Issues

5.1

Computing Related Legislation

5.1.1Data Protection Act (1998)5.1.2Computer Misuse Act (1990)5.1.3Copyright Designs & Patents Act (1988)5.1.4Creative Commons Licensing 5.1.5Regulation of Investigatory Powers Act (2000)

5.2

Moral & Ethical Issues

5.2.1Online Activity Tracking 5.2.2Censorship 5.2.3Positive Cultural Impacts 5.2.4Negative Cultural Impacts 5.2.5E-Waste 5.2.6Energy Consumption 5.2.7Positive Environmental Impact 5.2.8Layout, Colour Paradigms & Character Sets 5.2.9Computers in the Workplace 5.2.10Automated Decision-Making 5.2.11Artificial Intelligence 5.2.12Monitoring Behaviour 5.2.13Analysing Personal Information 5.2.14Piracy & Offensive Communication

6

Elements of Computational Thinking

6.1

Thinking Abstractly

6.1.1Abstraction

6.2

Thinking Ahead

6.2.1Inputs & Outputs

6.3

Thinking Procedurally

6.3.1Decomposition

6.4

Thinking Logically

6.4.1Pseudocode 6.4.2Flow Diagrams

6.5

Thinking Concurrently

6.5.1Concurrent Processing

7

Problem Solving & Programming

7.1

Programming Techniques

7.1.1Variables & Constants 7.1.2Comments 7.1.3Inputs & Outputs 7.1.4Subroutines 7.1.5Scope

7.2

Programming Construction

7.2.1Integrated Development Environments 7.2.2The Purpose of Testing 7.2.3Types of Testing 7.2.4Test Plans

8

Algorithms

8.1

Algorithms

8.1.1Interpreting Algorithms 8.1.2Correcting Algorithms 8.1.3Completing Algorithms 8.1.4Sort Algorithms 8.1.5Bubble Sort 8.1.6Insertion Sort 8.1.7Merge Sort 8.1.8Search Algorithms 8.1.9Linear Search 8.1.10Binary Search 8.1.11Quick Sort Algorithm 8.1.12A* Algorithm

Jump to other topics

1

Components of a Computer

2

Software & Software Development

2.1

Systems Software

2.1.1Operating Systems 2.1.2Managing Memory 2.1.3Paging 2.1.4Segmentation 2.1.5Device Management & Drivers 2.1.6Interrupts 2.1.7Interrupt Service Routine (ISR)2.1.8Scheduling 2.1.9Types of Scheduling 2.1.10Types of Operating System 2.1.11BIOS 2.1.12Virtual Machines

2.2

Applications Generation

2.2.1Applications Software 2.2.2Utilities 2.2.3Encryption Software 2.2.4Defragmentation Software 2.2.5Data Compression Software 2.2.6Backup Software 2.2.7Open Source Software 2.2.8Proprietary Software 2.2.9Licensing Issues 2.2.10Compilers 2.2.11Interpreters 2.2.12Assemblers 2.2.13Compiling a Program 2.2.14Lexical Analysis 2.2.15Compilation Stages 2.2.16Linkers, Loaders & Libraries

2.3

Software Development

2.3.1Algorithmic Thinking 2.3.2Waterfall Lifecycle 2.3.3Waterfall Lifecycle - Strengths & Weaknesses 2.3.4Agile Methodology 2.3.5Agile Methodology - Strengths & Weaknesses 2.3.6Extreme Programming 2.3.7Extreme Programming - Strengths & Weaknesses 2.3.8Spiral Methodology 2.3.9Spiral Methodology - Strengths & Weaknesses 2.3.10Rapid Application Development 2.3.11RAD - Strengths & Weaknesse

2.4

Types of Programming Language

2.4.1High Level Programming Languages 2.4.2Low Level Programming Languages 2.4.3Programming Paradigms 2.4.4Procedural Programming Languages 2.4.5Assembly 2.4.6Machine Code 2.4.7Modes of Addressing Memory 2.4.8Object-Oriented Languages 2.4.9Classes 2.4.10Objects 2.4.11Encapsulation 2.4.12Polymorphism

3

Exchanging Data

3.1

Compression, Encryption & Hashing

3.1.1Compression 3.1.2Run Length Encoding 3.1.3Dictionary Coding 3.1.4Encryption 3.1.5Symmetric Encyrption 3.1.6Hashing

3.2

Databases

3.2.1Records 3.2.2Databases 3.2.3Relational Databases 3.2.4Entity Relationship Modelling 3.2.5Managing Databases 3.2.6Normalisation 3.2.7SQL 3.2.8Principles of Data Storage 3.2.9Atomicity, Consistency, Isolation & Durability

3.3

Networks

3.4

Web Technologies

3.4.1HTML 3.4.2CSS 3.4.3JavaScript 3.4.4Search Engine Indexing 3.4.5PageRank Algorithm 3.4.6Server & Client-Side Processing

4

Data Types, Data Structures & Algorithms

4.1

Data Types

4.2

Data Structures

4.2.13D Arrays 4.2.2Linked List 4.2.3Queues 4.2.4Graphs 4.2.5Hash Tables 4.2.6Stacks 4.2.7Trees 4.2.8Binary Search Trees

4.3

Boolean Algebra

4.3.1Binary Systems 4.3.2Logic Circuits 4.3.3Boolean Operators 4.3.4Evaluating Expressions 4.3.5Boolean Logic 4.3.6Karnaugh Maps 4.3.7Boolean Identities 4.3.8Boolean Rules 4.3.9Flip Flops 4.3.10Adder Circuits

5

Legal, Moral, Cultural & Ethical Issues

5.1

Computing Related Legislation

5.1.1Data Protection Act (1998)5.1.2Computer Misuse Act (1990)5.1.3Copyright Designs & Patents Act (1988)5.1.4Creative Commons Licensing 5.1.5Regulation of Investigatory Powers Act (2000)

5.2

Moral & Ethical Issues

5.2.1Online Activity Tracking 5.2.2Censorship 5.2.3Positive Cultural Impacts 5.2.4Negative Cultural Impacts 5.2.5E-Waste 5.2.6Energy Consumption 5.2.7Positive Environmental Impact 5.2.8Layout, Colour Paradigms & Character Sets 5.2.9Computers in the Workplace 5.2.10Automated Decision-Making 5.2.11Artificial Intelligence 5.2.12Monitoring Behaviour 5.2.13Analysing Personal Information 5.2.14Piracy & Offensive Communication

6

Elements of Computational Thinking

6.1

Thinking Abstractly

6.1.1Abstraction

6.2

Thinking Ahead

6.2.1Inputs & Outputs

6.3

Thinking Procedurally

6.3.1Decomposition

6.4

Thinking Logically

6.4.1Pseudocode 6.4.2Flow Diagrams

6.5

Thinking Concurrently

6.5.1Concurrent Processing

7

Problem Solving & Programming

7.1

Programming Techniques

7.1.1Variables & Constants 7.1.2Comments 7.1.3Inputs & Outputs 7.1.4Subroutines 7.1.5Scope

7.2

Programming Construction

7.2.1Integrated Development Environments 7.2.2The Purpose of Testing 7.2.3Types of Testing 7.2.4Test Plans

8

Algorithms

8.1

Algorithms

8.1.1Interpreting Algorithms 8.1.2Correcting Algorithms 8.1.3Completing Algorithms 8.1.4Sort Algorithms 8.1.5Bubble Sort 8.1.6Insertion Sort 8.1.7Merge Sort 8.1.8Search Algorithms 8.1.9Linear Search 8.1.10Binary Search 8.1.11Quick Sort Algorithm 8.1.12A* Algorithm

Practice questions on Dictionary Coding

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1
Benefits of dictionary coding:Fill in the list
2
Which type of data is compressed using dictionary coding?Multiple choice
3
What happens when the dictionary coder finds a word that is not in the dictionary?Multiple choice

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Run Length Encoding

Encryption