1.2.5

Checksum & Echo Checks

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Checksum & Echo Checks

Checksum and echo checks are error detection methods that identify corrupted data during transmission, so it can be resent accurately.

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Why errors occur

  • Data transmission can be unreliable – errors can happen due to interference.
  • This can cause the data to be corrupted:
    • Data loss: Some bits of data go missing
    • Data gain: Extra, unwanted bits are added
    • Data change: Bits altered from a 0 to a 1, or vice versa
  • Error detection methods are used to find these corrupted data packets so they can be resent.
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Checksum

  • Checksum is an error detection method that works as a mathematical check.
    • The data is divided into blocks.
    • A calculation is performed on each block of data before being sent.
    • The result of this calculation is the checksum.
    • The checksum is added to the data block and both are sent to the receiver.
    • The same calculation is performed on the receiver's data block.
    • The new checksum is compared to the one sent by the sender.
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Outcome of checksum

  • If the two checksum values match → the data is correct.
  • If the two do not match → an error has occurred.
    • The data packet will be requested to be resent.
  • Checksum is widely used in networks and internet data transfer.
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Echo check

  • Echo check is a method that works by sending data back to the original sender to be verified.
    • Data is transmitted from the sender to the receiver.
    • The receiver then returns ("echoes") the same data block back to the sender.
    • The sender compares the data it sent (original data) with the data it received back.
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Outcome of echo check

  • If the two data blocks are identical → the data was transmitted successfully.
  • If there is a mismatch in data → an error has occurred and the data is sent again.
  • Echo check is less efficient than a checksum but simple to use.

Jump to other topics

1Computer Systems

1.1Data Representation

1.1.1Binary Numbers

1.1.2Negative Binary Numbers

1.1.3Hexadecimal

1.1.4Using Hexadecimal

1.1.5Converting Binary & Hexadecimal

1.1.6Converting Denary & Hexadecimal

1.1.7Capacity

1.1.8Calculating Capacity Requirements

1.1.9Binary in Computer Systems

1.1.10Data Compression

1.1.11Run Length Encoding

1.1.12File Formats

1.2Data Transmission

1.2.1Packet Switching

1.2.2Data Transmission

1.2.3Universal Serial Bus (USB)

1.2.4Parity Check

1.2.5Checksum & Echo Checks

1.2.6Encryption

1.3Hardware

1.3.1Elements of Computer Systems

1.3.2Types of Computer System

1.3.3Von Neumann Architecture

1.3.4The Fetch, Decode, Execute Cycle

1.3.5Factors Affecting CPU Performance

1.3.6Computational Logic

1.3.7Input Devices

1.3.82D & 3D Scanners

1.3.9Code Readers

1.3.10Solid State Storage

1.3.11Magnetic Storage

1.3.12Examples of Magnetic Storage

1.3.13Optical Storage

1.3.14Examples of Optical Storage

1.3.15Types of Optical disk

1.3.16Storage Requirements

1.3.17Translation - Compilers

1.3.18Translation - Interpreters

1.3.19Translation - Assemblers

1.3.20Acoustic Sensors

1.3.21Flow Sensors

1.3.22Gas Sensors

1.3.23Humidity Sensors

1.3.24Infrared Sensors

1.3.25Level Sensors

1.3.26Light Sensors

1.3.27Magnetic Field Sensors

1.3.28Moisture Sensors

1.3.29pH Sensors

1.3.30Pressure Sensors

1.3.31Proximity Sensors

1.3.32Temperature Sensors

1.3.33Network Hardware

1.4Software

1.4.1Operating Systems

1.4.2Interrupts

1.4.3High-Level Languages

1.4.4Low-Level Languages

1.5The Internet & its Uses

1.5.1The Internet

1.5.2Uniform Resource Locators (URLs)

1.5.3DNS

1.5.4HTML

1.5.5Cookies

1.5.6Web Hosting

1.5.7Digital Currency

1.6Cyber Security

1.6.1Forms of Attack

1.6.2Penetration Testing

1.6.3Types of Malware

1.6.4How Malware Spreads

1.6.5Protecting Against Malware

1.6.6Information Security

1.6.7Structured Query Language (SQL) Injection

1.6.8Firewalls

1.6.9Authentication: User Access Levels

1.6.10Authentication: Passwords

1.6.11Social Engineering

1.6.12Phishing

1.6.13Denial of Service Attacks

1.7Automated & Emerging Technologies

1.7.1Automated Systems

1.7.2Robotics

1.7.3Artificial Intelligence

2Algorithms, Programming & Logic

2.1Algorithm Design & Problem Solving

2.1.1Computational Thinking - Abstraction

2.1.2Computational Thinking - Decomposition

2.1.3Computational Thinking - Algorithmic Thinking

2.1.4Pseudocode

2.1.5Flow Diagrams

2.1.6Interpreting, Correcting & Completing Algorithm

2.1.7Correcting Algorithms

2.1.8Completing Algorithms

2.1.9Testing

2.1.10Types of Testing

2.1.11Test Plans

2.1.12Validation & Sanitation

2.1.13Authentication & Contingencies

2.2Programming

2.2.1Programming Fundamentals - Variables & Constants

2.2.2Programming Fundamentals - Comments

2.2.3Programming Fundamentals - Input & Output

2.2.4Data Types

2.2.5Casting

2.2.6Controlling Program Flow - Sequence

2.2.7Controlling Program Flow - Selection

2.2.8Controlling Program Flow - Iteration

2.2.9Modularity - Subroutines

2.2.10Modularity - Scope

2.2.11Arrays

2.3Databases

2.3.1Structuring Data - Records

2.3.2Structuring Data - Databases

2.3.3SQL

2.4Boolean Logic

2.4.1Binary Systems

2.4.2Logic Circuits

2.4.3Truth Tables

2.4.4Evaluating Expressions

2.4.5Boolean Operators

2.4.6End of Topic Test - Logic

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Parity Check

Encryption