NOTES FOR AS-LEVEL IT -
THEORETICAL (2022-2024)
Note: Units 4, 8 and 11 are skipped as they are categorised as practical units.
Unit 1:
Topic 1.1: Data and information
Data: Raw characters (e.g. Numbers, Letters, Symbols), sounds or images with non meaning
Information: Data items are given context and meaning (359 - Price in Pakistani rupees for the
Maths leak)
Direct Data Source: Primary source - Data collected for the purpose for which it will be used
+ Data is relevant because what is needed has been collected
+ Original source is known and trusted
+ Data likely to be up to date
+ Bias can be eliminated by asking specific questions
+ Data can be collected and presented in the format required
- Takes a long time to gather original data
- Large sample of statistical data difficult to collect for one-off purposes
Sources of Direct Data:
Questionnaires:
+ Useful with large number of respondents and statistical analysis being needed to carry
out on the results
+ Online questionnaires enable quicker analysis of data - filling in the data online and
entering directly into a database
+ Saves time - No further data entry by a third party is necessary
Interviews:
+ Can directly ask respondents to elaborate on their answers
Observations: What is happening during an activity
Data Logging: Using sensors
Indirect Data Source: Secondary source - Data was collected for a different purpose
+ Immediately available
+ More likely to be large samples available for statistical analysis
- Original source unknown, maybe unreliable
- Data may be out of date
- Original data may be biased due to its source
- Data unlikely to be in the format required, extracting data is difficult
, - Additional not required data will exist that may take time to sort through, Some data
required may not exist
Sources of Indirect Data:
- Electoral Register
- Businesses collecting personal information
Topic 1.2: Quality of information
Factors contributing to quality of information:
- Accuracy
- Relevance
- Age
- Level of Detail
- Completeness
Topic 1.3: Encryption
One specific type of coding is encryption.
Encryption: Data is scrambled so that the data cannot be understood.
Importance of Encryption:
- When sending strong sensitive data (e.g. personal information or a company’s sales
figures)
- Prevents hacker interception - Data may be lost or stolen when stored on social media
- Makes data difficult or impossible to read if accessed by an unauthorized person
Accessing encrypted data legitimately is called decryption.
Types of Encryption:
- Symmetric encryption: Oldest encryption method, It requires both sender and receiver to
possess a secret encryption and decryption key (private key), Secret key needs to be
sent to recipient, Could be intercepted upon transmission through post or internet at a
separate time
- Asymmetric encryption (Public-key cryptography): Public key available to anyone
wanting to send data, Private key is known only to the recipient, More processing than
symmetric -> Longer to decrypt the data, More secure than symmetric due to not having
to transmit the decryption key
Examples of using Asymmetric Encryption:
- Secure Sockets Layer (SSL)
- Transport Layer Security (TLS) - (both of them are referred to as SSL), Used for Online
Banking
, Process of Digital Certificates:
1. Digital certificate includes: Organisation name, Organisation that issued the certificate,
User’s email address, User’s country, User’s public key
2. Required to find a public key, which identify the user or server and provide the public key
3. Encrypted data required by recipient, computer will request digital certificate from the
sender. Public key is found within digital certificate.
Applications of Encryption:
Hard disk:
- Encrypts every single bit of data stored on a disk
- Encryption key is required to access any file on the desk
- Important to encrypt as these are portable storage media and so are susceptible to
being lost or stolen (e.g. USB Flash Memory and Backup Tapes)
- Data is usually accessed by entering a password OR using a fingerprint to unlock the
encryption
HTTPS (Hypertext Transfer Protocol Secure)
- HTTP (Hypertext Transfer Protocol) web pages’ data or the contents of the web page
can be read by anybody who intercepts web pages or data is sent over HTTP
- HTTPS is used for secure web pages. It uses TLS or SSL to encrypt and decrypt pages
and information sent and received by web users.
Email:
- Uses asymmetric encryption
- Recipients of emails must have the private key that matches the public key used to
encrypt the original email.
- For this to work, both the sender and receiver need to send each other a digitally-signed
message that will add the person’s digital certificate to the contact for that person.
- Encrypting an email will also encrypt any attachments.
Encryption protecting data:
- Only scrambles data so that it can’t be understood when found.
- Does not stop the data from being intercepted, stolen or lost.
- Strong 256-bit AES Encryption makes it virtually impossible for somebody to decrypt the
data -> Effectively protected from prying eyes.
Topic 1.4: Checking the accuracy of data
Validation:
- Presence check
- Range check
- Type check
- Length check
THEORETICAL (2022-2024)
Note: Units 4, 8 and 11 are skipped as they are categorised as practical units.
Unit 1:
Topic 1.1: Data and information
Data: Raw characters (e.g. Numbers, Letters, Symbols), sounds or images with non meaning
Information: Data items are given context and meaning (359 - Price in Pakistani rupees for the
Maths leak)
Direct Data Source: Primary source - Data collected for the purpose for which it will be used
+ Data is relevant because what is needed has been collected
+ Original source is known and trusted
+ Data likely to be up to date
+ Bias can be eliminated by asking specific questions
+ Data can be collected and presented in the format required
- Takes a long time to gather original data
- Large sample of statistical data difficult to collect for one-off purposes
Sources of Direct Data:
Questionnaires:
+ Useful with large number of respondents and statistical analysis being needed to carry
out on the results
+ Online questionnaires enable quicker analysis of data - filling in the data online and
entering directly into a database
+ Saves time - No further data entry by a third party is necessary
Interviews:
+ Can directly ask respondents to elaborate on their answers
Observations: What is happening during an activity
Data Logging: Using sensors
Indirect Data Source: Secondary source - Data was collected for a different purpose
+ Immediately available
+ More likely to be large samples available for statistical analysis
- Original source unknown, maybe unreliable
- Data may be out of date
- Original data may be biased due to its source
- Data unlikely to be in the format required, extracting data is difficult
, - Additional not required data will exist that may take time to sort through, Some data
required may not exist
Sources of Indirect Data:
- Electoral Register
- Businesses collecting personal information
Topic 1.2: Quality of information
Factors contributing to quality of information:
- Accuracy
- Relevance
- Age
- Level of Detail
- Completeness
Topic 1.3: Encryption
One specific type of coding is encryption.
Encryption: Data is scrambled so that the data cannot be understood.
Importance of Encryption:
- When sending strong sensitive data (e.g. personal information or a company’s sales
figures)
- Prevents hacker interception - Data may be lost or stolen when stored on social media
- Makes data difficult or impossible to read if accessed by an unauthorized person
Accessing encrypted data legitimately is called decryption.
Types of Encryption:
- Symmetric encryption: Oldest encryption method, It requires both sender and receiver to
possess a secret encryption and decryption key (private key), Secret key needs to be
sent to recipient, Could be intercepted upon transmission through post or internet at a
separate time
- Asymmetric encryption (Public-key cryptography): Public key available to anyone
wanting to send data, Private key is known only to the recipient, More processing than
symmetric -> Longer to decrypt the data, More secure than symmetric due to not having
to transmit the decryption key
Examples of using Asymmetric Encryption:
- Secure Sockets Layer (SSL)
- Transport Layer Security (TLS) - (both of them are referred to as SSL), Used for Online
Banking
, Process of Digital Certificates:
1. Digital certificate includes: Organisation name, Organisation that issued the certificate,
User’s email address, User’s country, User’s public key
2. Required to find a public key, which identify the user or server and provide the public key
3. Encrypted data required by recipient, computer will request digital certificate from the
sender. Public key is found within digital certificate.
Applications of Encryption:
Hard disk:
- Encrypts every single bit of data stored on a disk
- Encryption key is required to access any file on the desk
- Important to encrypt as these are portable storage media and so are susceptible to
being lost or stolen (e.g. USB Flash Memory and Backup Tapes)
- Data is usually accessed by entering a password OR using a fingerprint to unlock the
encryption
HTTPS (Hypertext Transfer Protocol Secure)
- HTTP (Hypertext Transfer Protocol) web pages’ data or the contents of the web page
can be read by anybody who intercepts web pages or data is sent over HTTP
- HTTPS is used for secure web pages. It uses TLS or SSL to encrypt and decrypt pages
and information sent and received by web users.
Email:
- Uses asymmetric encryption
- Recipients of emails must have the private key that matches the public key used to
encrypt the original email.
- For this to work, both the sender and receiver need to send each other a digitally-signed
message that will add the person’s digital certificate to the contact for that person.
- Encrypting an email will also encrypt any attachments.
Encryption protecting data:
- Only scrambles data so that it can’t be understood when found.
- Does not stop the data from being intercepted, stolen or lost.
- Strong 256-bit AES Encryption makes it virtually impossible for somebody to decrypt the
data -> Effectively protected from prying eyes.
Topic 1.4: Checking the accuracy of data
Validation:
- Presence check
- Range check
- Type check
- Length check
