Error Checking (Cambridge (CIE) IGCSE Computer Science)

Revision Note

Robert Hampton

Written by: Robert Hampton

Reviewed by: James Woodhouse

Why Errors Occur

Why do errors occur?

  • Errors can occur using wired or wireless technology due to interference 

  • Examples of interference include wire degradation or electrical fields changing the signal

  • Results of interference include:

    • Data loss - data is lost in transmission

    • Data gain - additional data is received

    • Data change - some bits have been changed or flipped

  • Wireless technology uses radio signals or other electromagnetic signals to transmit data

    • These signals can be blocked by physical barriers such as buildings, walls, cars or other objects

    • Interference can be caused by bad weather such as rain or clouds, or by other wireless signals or electromagnetic radiation 

  • Wired technology carries more chance of causing an error as physical components can be damaged, degrade or receive interference from outside signals

    • Data loss can also occur from interruptions to data transmission such as a blocked signal or if the transmission is intermittent

Why check for errors?

  • Computers expect data in certain formats

    • A format is a way of arranging the data so that it can be easily understood by people and by computers

    • People agree to certain formats so that systems work more efficiently and there is little chance of misunderstanding each other

  • An example of a format is date and time

  • Date and time can have multiple formats such as:

    • 13/04/14 (DD/MM/YY)

    • 12/31/2020 (MM/DD/YYYY)

    • Jul-04-16 (MMM/DD/YY)

  • If data is not as expected, things can go wrong

  • For example, if a receiver expected to receive a date in format DD/MM/YY as 03/04/17 but received 04/03/17, did the sender mean 3rd April 2017 or 4th March 2017?

  • An error or corruption occurs when data received is not as expected and therefore is difficult or impossible to process

Worked Example

Alex receives an email over a wireless connection from a work colleague containing an important document. 

Identify what interference Alex could experience when sending this email and identify the outcomes of interference.

Further explain why Alex should check to make sure the document contains no errors.

[4]

Answer

  • Weather conditions or physical barriers such as building can affect signals, for example bits could be flipped in the document making it hard to understand the original meaning [1]

  • Alex should be aware that interference can cause wirelessly received data to contain errors or corruption [1]

  • Data could be lost, additional data could be gained or data could be changed [1]

  • As Alex received an important work document they need to check for errors so that their work is unaffected and they do not receive incorrect information [1]

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Robert Hampton

Author: Robert Hampton

Expertise: Computer Science Content Creator

Rob has over 16 years' experience teaching Computer Science and ICT at KS3 & GCSE levels. Rob has demonstrated strong leadership as Head of Department since 2012 and previously supported teacher development as a Specialist Leader of Education, empowering departments to excel in Computer Science. Beyond his tech expertise, Robert embraces the virtual world as an avid gamer, conquering digital battlefields when he's not coding.

James Woodhouse

Author: James Woodhouse

Expertise: Computer Science

James graduated from the University of Sunderland with a degree in ICT and Computing education. He has over 14 years of experience both teaching and leading in Computer Science, specialising in teaching GCSE and A-level. James has held various leadership roles, including Head of Computer Science and coordinator positions for Key Stage 3 and Key Stage 4. James has a keen interest in networking security and technologies aimed at preventing security breaches.