Source: https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-3-1-binary-systems [Revision notes](https://senecalearning.com/en-gb/revision-notes.md) › [IGCSE](https://senecalearning.com/en-gb/revision-notes/igcse.md) › [Computer Science](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science.md) › [Edexcel IGCSE](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse.md) › Binary Systems # Binary Systems Computer Science: Edexcel IGCSE, topic 4.3.1 ## Binary Systems Computer systems store and process data as binary digits. ### Why use binary form? ![Why use binary form?](https://image-v2.cdn.app.senecalearning.com/2018-07/31c77d00-497e-4e13-9319-bd43c2c1c731/Computer-Binary-1-0-Byte-.jpg) - Underneath the surface computers are electrical devices that process information by controlling the flow of electricity through billions of wires and transistors (electrical switches) inside the central processing unit and other components. - The presence of electricity represents a 1, and an absence of electricity represents a 0. ### The transistor ![The transistor](https://image-v2.cdn.app.senecalearning.com/2018-08/e6a4bf35-5519-428e-bd17-35c9dac309ca/transistor-electircal-tool-.jpg) - Transistors are electrical components made from semiconductor materials that can act as electrically-controlled switches. - Transistors can be used to temporarily store data, for example in some forms of primary storage (memory). ### Transistors in the CPU ![Transistors in the CPU](https://image-v2.cdn.app.senecalearning.com/2018-07/b43201c6-4785-4a02-8529-99b5ab9f8ea8/Computer-Cache-Memory-CPU-.jpg) - Inside a Central Processing Unit (CPU), transistors are arranged into circuits to perform operations such as calculations when electricity is passed through them. - For example, transistors can be arranged to form an 'adder' circuit that can accept two binary numbers, and output the sum of their values. - Modern CPUs contain over 3 billion transistors, allowing them to perform billions of calculations per second. ## Test yourself on Binary Systems - What represents a 1 in most modern computers? [Practise this topic for free](https://app.senecalearning.com/classroom/course/40426d0e-f017-490c-a2b3-c98a77d973bd/section/dd1af6d5-9f0a-4c40-b23a-ae43da7c8fc4/session) - Previous topic: [4.2.25 End of Topic Test - Hardware](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-25-end-of-topic-test-hardware.md) - Next topic: [4.3.2 Logic Circuits](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-3-2-logic-circuits.md) ## Computer Science: Edexcel IGCSE contents ### 1 Problem Solving - 1.1 Algorithms - [1.1.1 Algorithm Thinking](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-1-1-algorithm-thinking.md) - [1.1.2 Interpreting Algorithms](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-1-2-interpreting-algorithms.md) - [1.1.3 Expressing Algorithms - Pseudocode](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-1-3-expressing-algorithms-pseudocode.md) - [1.1.4 Expressing Algorithms - Flow Charts](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-1-4-expressing-algorithms-flow-charts.md) - [1.1.5 Correcting Algorithms](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-1-5-correcting-algorithms.md) - [1.1.6 Completing Algorithms](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-1-6-completing-algorithms.md) - [1.1.7 Search Algorithms](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-1-7-search-algorithms.md) - [1.1.8 Linear Search](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-1-8-linear-search.md) - [1.1.9 Binary Search](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-1-9-binary-search.md) - [1.1.10 Sort Algorithms](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-1-10-sort-algorithms.md) - [1.1.11 Bubble Sort](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-1-11-bubble-sort.md) - [1.1.12 Merge Sort](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-1-12-merge-sort.md) - 1.2 Decomposition & Abstraction - [1.2.1 Computational Thinking - Abstraction](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-2-1-computational-thinking-abstraction.md) - [1.2.2 Computational Thinking - Decomposition](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-2-2-computational-thinking-decomposition.md) - [1.2.3 End of Topic Test - Algorithms](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/1-2-3-end-of-topic-test-algorithms.md) ### 2 Programming - 2.1 Develop Code - [2.1.1 Maintainability](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-1-1-maintainability.md) - [2.1.2 Comments](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-1-2-comments.md) - [2.1.3 Exceptions](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-1-3-exceptions.md) - [2.1.4 Syntax Error](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-1-4-syntax-error.md) - [2.1.5 Logic Error](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-1-5-logic-error.md) - [2.1.6 Runtime Error](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-1-6-runtime-error.md) - [2.1.7 Purpose of Testing](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-1-7-purpose-of-testing.md) - [2.1.8 Test Plans](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-1-8-test-plans.md) - 2.2 Constructs - [2.2.1 Selection](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-2-1-selection.md) - [2.2.2 Sequence](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-2-2-sequence.md) - [2.2.3 Iteration](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-2-3-iteration.md) - 2.3 Data Types & Structures - [2.3.1 Variables & Constants](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-3-1-variables-and-constants.md) - [2.3.2 Scope](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-3-2-scope.md) - [2.3.3 Data Types](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-3-3-data-types.md) - [2.3.4 Casting](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-3-4-casting.md) - [2.3.5 Data Structures - Arrays](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-3-5-data-structures-arrays.md) - [2.3.6 Data Structures - 2D Arrays](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-3-6-data-structures-2d-arrays.md) - [2.3.7 Data Structures - Strings](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-3-7-data-structures-strings.md) - [2.3.8 Data Structures - Records](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-3-8-data-structures-records.md) - 2.4 Input / Output - [2.4.1 Input and Output](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-4-1-input-and-output.md) - [2.4.2 Validation and Sanitation](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-4-2-validation-and-sanitation.md) - [2.4.3 Files](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-4-3-files.md) - [2.4.4 File Handling](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-4-4-file-handling.md) - 2.5 Operators - [2.5.1 Arithmetic Operators](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-5-1-arithmetic-operators.md) - [2.5.2 Relational Operators](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-5-2-relational-operators.md) - [2.5.3 Boolean Operators](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-5-3-boolean-operators.md) - 2.6 Subprograms - [2.6.1 Modularity](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-6-1-modularity.md) - [2.6.2 End of Topic Test - Programming](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/2-6-2-end-of-topic-test-programming.md) ### 3 Data - 3.1 Binary - [3.1.1 Number Bases](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-1-1-number-bases.md) - [3.1.2 Negative Binary Numbers](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-1-2-negative-binary-numbers.md) - [3.1.3 Binary Addition](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-1-3-binary-addition.md) - [3.1.4 Binary Shifts](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-1-4-binary-shifts.md) - 3.2 Data Representation - [3.2.1 Representing Text](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-2-1-representing-text.md) - [3.2.2 ASCII](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-2-2-ascii.md) - [3.2.3 Unicode](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-2-3-unicode.md) - [3.2.4 Representing Images](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-2-4-representing-images.md) - [3.2.5 Representing Sound](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-2-5-representing-sound.md) - 3.3 Data Storage & Compression - [3.3.1 Capacity](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-3-1-capacity.md) - [3.3.2 Calculating Capacity Requirements](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-3-2-calculating-capacity-requirements.md) - [3.3.3 Data Compression](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-3-3-data-compression.md) - [3.3.4 Run Length Encoding](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-3-4-run-length-encoding.md) - 3.4 Encryption - [3.4.1 Encryption](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-4-1-encryption.md) - [3.4.2 Caesar Cipher](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-4-2-caesar-cipher.md) - [3.4.3 Ciphers](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-4-3-ciphers.md) - 3.5 Databases - [3.5.1 Databases](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-5-1-databases.md) - [3.5.2 End of Topic Test - Data & Representation](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/3-5-2-end-of-topic-test-data-and-representation.md) ### 4 Computers - 4.1 Machines & Computational Modelling - [4.1.1 Computational Models](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-1-1-computational-models.md) - [4.1.2 Input-Process-Output Model](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-1-2-input-process-output-model.md) - 4.2 Hardware - [4.2.1 Elements of Computer Systems](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-1-elements-of-computer-systems.md) - [4.2.2 Types of Computer Systems](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-2-types-of-computer-systems.md) - [4.2.3 Memory - RAM](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-3-memory-ram.md) - [4.2.4 Memory - ROM](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-4-memory-rom.md) - [4.2.5 Memory - Cache](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-5-memory-cache.md) - [4.2.6 Running Out of Memory](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-6-running-out-of-memory.md) - [4.2.7 Virtual Memory](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-7-virtual-memory.md) - [4.2.8 Magnetic Storage](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-8-magnetic-storage.md) - [4.2.9 Properties of Magnetic Media](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-9-properties-of-magnetic-media.md) - [4.2.10 Examples of Magnetic Storage](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-10-examples-of-magnetic-storage.md) - [4.2.11 Solid State Storage](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-11-solid-state-storage.md) - [4.2.12 Properties of Solid State Media](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-12-properties-of-solid-state-media.md) - [4.2.13 Optical Storage](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-13-optical-storage.md) - [4.2.14 Properties of Optical Storage](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-14-properties-of-optical-storage.md) - [4.2.15 Examples of Optical Storage](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-15-examples-of-optical-storage.md) - [4.2.16 Types of Optical Disk](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-16-types-of-optical-disk.md) - [4.2.17 Von Neumann Architecture](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-17-von-neumann-architecture.md) - [4.2.18 Registers of the Central Processing Unit (CPU)](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-18-registers-of-the-central-processing-unit-cpu.md) - [4.2.19 Fetch-Decode-Execute Cycle](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-19-fetch-decode-execute-cycle.md) - [4.2.20 Factors Affecting CPU Performance](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-20-factors-affecting-cpu-performance.md) - [4.2.21 The Cloud](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-21-the-cloud.md) - [4.2.22 How the Cloud Works](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-22-how-the-cloud-works.md) - [4.2.23 The Cloud - Pros](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-23-the-cloud-pros.md) - [4.2.24 The Cloud - Cons](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-24-the-cloud-cons.md) - [4.2.25 End of Topic Test - Hardware](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-2-25-end-of-topic-test-hardware.md) - 4.3 Logic - [4.3.1 Binary Systems](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-3-1-binary-systems.md) - [4.3.2 Logic Circuits](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-3-2-logic-circuits.md) - [4.3.3 Boolean Logic](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-3-3-boolean-logic.md) - [4.3.4 End of Topic Test - Logic](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-3-4-end-of-topic-test-logic.md) - 4.4 Software - [4.4.1 Operating Systems](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-4-1-operating-systems.md) - [4.4.2 User Interface Managetment](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-4-2-user-interface-managetment.md) - [4.4.3 Memory and Process Management](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-4-3-memory-and-process-management.md) - [4.4.4 File Management](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-4-4-file-management.md) - [4.4.5 Device Management](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-4-5-device-management.md) - [4.4.6 User Management](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-4-6-user-management.md) - [4.4.7 Encryption Software](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-4-7-encryption-software.md) - [4.4.8 Defragmentation Software](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-4-8-defragmentation-software.md) - [4.4.9 Data Compression Software](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-4-9-data-compression-software.md) - [4.4.10 Backup Software](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-4-10-backup-software.md) - 4.5 Programming Languages - [4.5.1 High Level Languages](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-5-1-high-level-languages.md) - [4.5.2 Low Level Languages](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-5-2-low-level-languages.md) - [4.5.3 Translators - Compilers](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-5-3-translators-compilers.md) - [4.5.4 Translators - Interpreters](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-5-4-translators-interpreters.md) - [4.5.5 Translators - Assemblers](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-5-5-translators-assemblers.md) - [4.5.6 End of Topic Test - Translation & Representation](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/4-5-6-end-of-topic-test-translation-and-representation.md) ### 5 Communication & The Internet - 5.1 Networks - [5.1.1 Benefits of Networks](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-1-benefits-of-networks.md) - [5.1.2 Network Performance](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-2-network-performance.md) - [5.1.3 Types of Network](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-3-types-of-network.md) - [5.1.4 Client-Server Model](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-4-client-server-model.md) - [5.1.5 Pros of Client-Server Model](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-5-pros-of-client-server-model.md) - [5.1.6 Cons of Client-Server Model](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-6-cons-of-client-server-model.md) - [5.1.7 Peer-to-Peer Model](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-7-peer-to-peer-model.md) - [5.1.8 Pros of Peer-to-Peer Model](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-8-pros-of-peer-to-peer-model.md) - [5.1.9 Cons of Peer-to-Peer Model](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-9-cons-of-peer-to-peer-model.md) - [5.1.10 Network Hardware](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-10-network-hardware.md) - [5.1.11 Transmission Media](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-11-transmission-media.md) - [5.1.12 WiFi](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-12-wifi.md) - [5.1.13 WiFi Frequency and Channels](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-13-wifi-frequency-and-channels.md) - [5.1.14 WiFi Encryption](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-14-wifi-encryption.md) - [5.1.15 Network Protocols](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-15-network-protocols.md) - [5.1.16 Transmission Protocols](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-16-transmission-protocols.md) - [5.1.17 Web Protocols](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-17-web-protocols.md) - [5.1.18 Email Protocols](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-18-email-protocols.md) - [5.1.19 Layers](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-19-layers.md) - [5.1.20 TCP and OSI Models](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-20-tcp-and-osi-models.md) - [5.1.21 Advantages of Layering](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-21-advantages-of-layering.md) - [5.1.22 Topology - Star](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-22-topology-star.md) - [5.1.23 Topology - Mesh](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-23-topology-mesh.md) - [5.1.24 Topology - Ring](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-24-topology-ring.md) - [5.1.25 Topology - Bus](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-25-topology-bus.md) - [5.1.26 End of Topic Test - Networks](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-1-26-end-of-topic-test-networks.md) - 5.2 Network Security - [5.2.1 User Access Levels](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-2-1-user-access-levels.md) - [5.2.2 Encryption](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-2-2-encryption.md) - [5.2.3 Protecting Against Malware](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-2-3-protecting-against-malware.md) - [5.2.4 Firewalls](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-2-4-firewalls.md) - [5.2.5 Forms of Attack](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-2-5-forms-of-attack.md) - [5.2.6 Penetration Testing](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-2-6-penetration-testing.md) - [5.2.7 Malware](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-2-7-malware.md) - [5.2.8 How Malware Spreads](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-2-8-how-malware-spreads.md) - [5.2.9 Social Engineering](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-2-9-social-engineering.md) - [5.2.10 Protecting Against Social Engineering](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-2-10-protecting-against-social-engineering.md) - [5.2.11 Phishing](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-2-11-phishing.md) - [5.2.12 Network Administration](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-2-12-network-administration.md) - [5.2.13 Network Forensics](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-2-13-network-forensics.md) - 5.3 The Internet & the World Wide Web - [5.3.1 IP Addresses](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-3-1-ip-addresses.md) - [5.3.2 Types of IP Address](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-3-2-types-of-ip-address.md) - [5.3.3 MAC Addresses](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-3-3-mac-addresses.md) - [5.3.4 Packet Switching](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-3-4-packet-switching.md) - [5.3.5 How Do Packets Get Routed?](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-3-5-how-do-packets-get-routed.md) - [5.3.6 Did My Data Arrive Safely?](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-3-6-did-my-data-arrive-safely.md) - [5.3.7 The Internet](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-3-7-the-internet.md) - [5.3.8 URLs](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-3-8-urls.md) - [5.3.9 DNS](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-3-9-dns.md) - [5.3.10 Web Hosting](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-3-10-web-hosting.md) - [5.3.11 End of Topic Test - Security](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/5-3-11-end-of-topic-test-security.md) ### 6 The Bigger Picture - 6.1 Emerging Trends, Issues & Impact - [6.1.1 E-Waste](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-1-e-waste.md) - [6.1.2 Energy Consumption](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-2-energy-consumption.md) - [6.1.3 Positive Environmental Impact](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-3-positive-environmental-impact.md) - [6.1.4 Ethical Issues - The Digital Divide](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-4-ethical-issues-the-digital-divide.md) - [6.1.5 Ethical Issues - Net Neutrality](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-5-ethical-issues-net-neutrality.md) - [6.1.6 Ethical Issues - Working Conditions](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-6-ethical-issues-working-conditions.md) - [6.1.7 Ethical Issues - Censorship](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-7-ethical-issues-censorship.md) - [6.1.8 Online Activity Tracking](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-8-online-activity-tracking.md) - [6.1.9 The Internet of Things](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-9-the-internet-of-things.md) - [6.1.10 Positive Cultural Impacts](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-10-positive-cultural-impacts.md) - [6.1.11 Negative Cultural Impacts](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-11-negative-cultural-impacts.md) - [6.1.12 Data Protection Act](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-12-data-protection-act.md) - [6.1.13 Computer Misuse Act](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-13-computer-misuse-act.md) - [6.1.14 Copyright Designs and Parents Act](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-14-copyright-designs-and-parents-act.md) - [6.1.15 Creative Commons Licensing](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-15-creative-commons-licensing.md) - [6.1.16 Freedom of Information Act](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-16-freedom-of-information-act.md) - [6.1.17 Open Source Software](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-17-open-source-software.md) - [6.1.18 Proprietary Software](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-18-proprietary-software.md) - [6.1.19 Licensing Issues](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-19-licensing-issues.md) - [6.1.20 End of Topic Test - Software & Issues](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/edexcel-igcse/6-1-20-end-of-topic-test-software-and-issues.md)