Source: https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-4-1-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) › [Cambridge International](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international.md) › Binary Systems # Binary Systems Computer Science: Cambridge International GCSE, topic 2.4.1 ## 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/a91ea2d8-1487-49f1-a3c1-17e86c67462e/section/535f12a4-0106-45e1-b23f-f09a24819545/session) - Previous topic: [2.3.3 SQL](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-3-3-sql.md) - Next topic: [2.4.2 Logic Circuits](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-4-2-logic-circuits.md) ## Computer Science: Cambridge International GCSE contents ### 1 Computer Systems - 1.1 Data Representation - [1.1.1 Binary Numbers](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-1-1-binary-numbers.md) - [1.1.2 Negative Binary Numbers](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-1-2-negative-binary-numbers.md) - [1.1.3 Hexadecimal](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-1-3-hexadecimal.md) - [1.1.4 Using Hexadecimal](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-1-4-using-hexadecimal.md) - [1.1.5 Converting Binary & Hexadecimal](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-1-5-converting-binary-and-hexadecimal.md) - [1.1.6 Converting Denary & Hexadecimal](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-1-6-converting-denary-and-hexadecimal.md) - [1.1.7 Capacity](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-1-7-capacity.md) - [1.1.8 Calculating Capacity Requirements](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-1-8-calculating-capacity-requirements.md) - [1.1.9 Binary in Computer Systems](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-1-9-binary-in-computer-systems.md) - [1.1.10 Data Compression](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-1-10-data-compression.md) - [1.1.11 Run Length Encoding](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-1-11-run-length-encoding.md) - [1.1.12 File Formats](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-1-12-file-formats.md) - 1.2 Data Transmission - [1.2.1 Packet Switching](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-2-1-packet-switching.md) - [1.2.2 Data Transmission](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-2-2-data-transmission.md) - [1.2.3 Universal Serial Bus (USB)](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-2-3-universal-serial-bus-usb.md) - [1.2.4 Parity Check](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-2-4-parity-check.md) - [1.2.5 Checksum & Echo Checks](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-2-5-checksum-and-echo-checks.md) - [1.2.6 Encryption](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-2-6-encryption.md) - 1.3 Hardware - [1.3.1 Elements of Computer Systems](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-1-elements-of-computer-systems.md) - [1.3.2 Types of Computer System](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-2-types-of-computer-system.md) - [1.3.3 Von Neumann Architecture](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-3-von-neumann-architecture.md) - [1.3.4 The Fetch, Decode, Execute Cycle](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-4-the-fetch-decode-execute-cycle.md) - [1.3.5 Factors Affecting CPU Performance](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-5-factors-affecting-cpu-performance.md) - [1.3.6 Computational Logic](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-6-computational-logic.md) - [1.3.7 Input Devices](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-7-input-devices.md) - [1.3.8 2D & 3D Scanners](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-8-2d-and-3d-scanners.md) - [1.3.9 Code Readers](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-9-code-readers.md) - [1.3.10 Solid State Storage](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-10-solid-state-storage.md) - [1.3.11 Magnetic Storage](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-11-magnetic-storage.md) - [1.3.12 Examples of Magnetic Storage](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-12-examples-of-magnetic-storage.md) - [1.3.13 Optical Storage](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-13-optical-storage.md) - [1.3.14 Examples of Optical Storage](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-14-examples-of-optical-storage.md) - [1.3.15 Types of Optical disk](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-15-types-of-optical-disk.md) - [1.3.16 Storage Requirements](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-16-storage-requirements.md) - [1.3.17 Translation - Compilers](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-17-translation-compilers.md) - [1.3.18 Translation - Interpreters](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-18-translation-interpreters.md) - [1.3.19 Translation - Assemblers](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-19-translation-assemblers.md) - [1.3.20 Acoustic Sensors](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-20-acoustic-sensors.md) - [1.3.21 Flow Sensors](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-21-flow-sensors.md) - [1.3.22 Gas Sensors](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-22-gas-sensors.md) - [1.3.23 Humidity Sensors](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-23-humidity-sensors.md) - [1.3.24 Infrared Sensors](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-24-infrared-sensors.md) - [1.3.25 Level Sensors](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-25-level-sensors.md) - [1.3.26 Light Sensors](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-26-light-sensors.md) - [1.3.27 Magnetic Field Sensors](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-27-magnetic-field-sensors.md) - [1.3.28 Moisture Sensors](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-28-moisture-sensors.md) - [1.3.29 pH Sensors](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-29-ph-sensors.md) - [1.3.30 Pressure Sensors](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-30-pressure-sensors.md) - [1.3.31 Proximity Sensors](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-31-proximity-sensors.md) - [1.3.32 Temperature Sensors](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-32-temperature-sensors.md) - [1.3.33 Network Hardware](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-3-33-network-hardware.md) - 1.4 Software - [1.4.1 Operating Systems](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-4-1-operating-systems.md) - [1.4.2 Interrupts](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-4-2-interrupts.md) - [1.4.3 High-Level Languages](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-4-3-high-level-languages.md) - [1.4.4 Low-Level Languages](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-4-4-low-level-languages.md) - 1.5 The Internet & its Uses - [1.5.1 The Internet](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-5-1-the-internet.md) - [1.5.2 Uniform Resource Locators (URLs)](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-5-2-uniform-resource-locators-urls.md) - [1.5.3 DNS](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-5-3-dns.md) - [1.5.4 HTML](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-5-4-html.md) - [1.5.5 Cookies](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-5-5-cookies.md) - [1.5.6 Web Hosting](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-5-6-web-hosting.md) - [1.5.7 Digital Currency](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-5-7-digital-currency.md) - 1.6 Cyber Security - [1.6.1 Forms of Attack](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-6-1-forms-of-attack.md) - [1.6.2 Penetration Testing](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-6-2-penetration-testing.md) - [1.6.3 Types of Malware](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-6-3-types-of-malware.md) - [1.6.4 How Malware Spreads](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-6-4-how-malware-spreads.md) - [1.6.5 Protecting Against Malware](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-6-5-protecting-against-malware.md) - [1.6.6 Information Security](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-6-6-information-security.md) - [1.6.7 Structured Query Language (SQL) Injection](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-6-7-structured-query-language-sql-injection.md) - [1.6.8 Firewalls](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-6-8-firewalls.md) - [1.6.9 Authentication: User Access Levels](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-6-9-authentication-user-access-levels.md) - [1.6.10 Authentication: Passwords](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-6-10-authentication-passwords.md) - [1.6.11 Social Engineering](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-6-11-social-engineering.md) - [1.6.12 Phishing](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-6-12-phishing.md) - [1.6.13 Denial of Service Attacks](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-6-13-denial-of-service-attacks.md) - 1.7 Automated & Emerging Technologies - [1.7.1 Automated Systems](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-7-1-automated-systems.md) - [1.7.2 Robotics](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-7-2-robotics.md) - [1.7.3 Artificial Intelligence](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/1-7-3-artificial-intelligence.md) ### 2 Algorithms, Programming & Logic - 2.1 Algorithm Design & Problem Solving - [2.1.1 Computational Thinking - Abstraction](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-1-1-computational-thinking-abstraction.md) - [2.1.2 Computational Thinking - Decomposition](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-1-2-computational-thinking-decomposition.md) - [2.1.3 Computational Thinking - Algorithmic Thinking](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-1-3-computational-thinking-algorithmic-thinking.md) - [2.1.4 Pseudocode](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-1-4-pseudocode.md) - [2.1.5 Flow Diagrams](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-1-5-flow-diagrams.md) - [2.1.6 Interpreting, Correcting & Completing Algorithm](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-1-6-interpreting-correcting-and-completing-algorithm.md) - [2.1.7 Correcting Algorithms](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-1-7-correcting-algorithms.md) - [2.1.8 Completing Algorithms](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-1-8-completing-algorithms.md) - [2.1.9 Testing](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-1-9-testing.md) - [2.1.10 Types of Testing](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-1-10-types-of-testing.md) - [2.1.11 Test Plans](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-1-11-test-plans.md) - [2.1.12 Validation & Sanitation](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-1-12-validation-and-sanitation.md) - [2.1.13 Authentication & Contingencies](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-1-13-authentication-and-contingencies.md) - 2.2 Programming - [2.2.1 Programming Fundamentals - Variables & Constants](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-2-1-programming-fundamentals-variables-and-constants.md) - [2.2.2 Programming Fundamentals - Comments](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-2-2-programming-fundamentals-comments.md) - [2.2.3 Programming Fundamentals - Input & Output](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-2-3-programming-fundamentals-input-and-output.md) - [2.2.4 Data Types](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-2-4-data-types.md) - [2.2.5 Casting](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-2-5-casting.md) - [2.2.6 Controlling Program Flow - Sequence](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-2-6-controlling-program-flow-sequence.md) - [2.2.7 Controlling Program Flow - Selection](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-2-7-controlling-program-flow-selection.md) - [2.2.8 Controlling Program Flow - Iteration](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-2-8-controlling-program-flow-iteration.md) - [2.2.9 Modularity - Subroutines](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-2-9-modularity-subroutines.md) - [2.2.10 Modularity - Scope](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-2-10-modularity-scope.md) - [2.2.11 Arrays](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-2-11-arrays.md) - 2.3 Databases - [2.3.1 Structuring Data - Records](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-3-1-structuring-data-records.md) - [2.3.2 Structuring Data - Databases](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-3-2-structuring-data-databases.md) - [2.3.3 SQL](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-3-3-sql.md) - 2.4 Boolean Logic - [2.4.1 Binary Systems](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-4-1-binary-systems.md) - [2.4.2 Logic Circuits](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-4-2-logic-circuits.md) - [2.4.3 Truth Tables](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-4-3-truth-tables.md) - [2.4.4 Evaluating Expressions](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-4-4-evaluating-expressions.md) - [2.4.5 Boolean Operators](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-4-5-boolean-operators.md) - [2.4.6 End of Topic Test - Logic](https://senecalearning.com/en-gb/revision-notes/igcse/computer-science/cambridge-international/2-4-6-end-of-topic-test-logic.md)