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Summary Information Technology AS-Levels, missing topics 4 and 8
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Information Technology A-Levels, missing topics 4 and 8, contains 1-3, 5-7, 10 and 11, Mostly for Cambridge Students
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Data and Information Data is a set of numbers, text, pictures, videos etc. that have no set meaning or context
information is data that have been given meaning and context after it has been processed by
a computer or user.
Direct and indirect Data
Direct-Data
o that has been collected from the source for a specific purpose and used for only that
purpose
Indirect
o Data that has been collected from third party sources instead of the original sources
and isn’t used for the purpose that it was originally collected for
Direct sources
Questionnaires-Questionaries are set of arranged questions that can be distributed to
people to get answers from them, they are easy to distribute, complete and collect as they
are user friendly.
interview-is a one-to-one meeting between the interviewee and the interviewer, in which
the interviewer would ask questions, to get direct opinions/facts from the interviewer, these
can be open ended and close ended questions, questions can be expanded on by the
interviewer and more answers can be gotten.
Observation- a method of gathering data by collectors by watching what happens in a given
situation
Data logging- using sensors and computers to collect data, which is analysed, saved and
output in graphs, charts, etc., most commonly used in scientific experiments, where human
intervention is not suitable.
Indirect sources
Electoral registers- Registers that hold record of citizens that are eligible to vote in an
election, they have citizen details such as name, address, age etc. which have some details
removed from the open version of the register
Third Party- a method of collecting data is from third party sources, there are companies
that collect an individual’s personal information and sell it to each other and to advertisers.
Business’s often ask customers if personal data could be shared with other organisations
after the customer use/buy their product
Pros and cons of direct
Pros
source of data is known so data can be trusted
All data gathered is gathered only for your purpose
Likely to be up to date
Data can be presented in the format required
Data can be sold later as indirect after using it for the particular purpose
, Cons
Time taking and costs a lot
Data logging Equipment can be expensive
Large samples can be difficult to collect
Pros and cons of Indirect
Pros
Readily available
Costs less than getting direct data as it takes less time
Mostly available in large samples
Cons
Less reliable as source is unknown
Would contain information that is not required
Might be out of date
Might be difficult to extract data as it would be in the wrong format
Quality of Information
Accuracy
If the data collected is inaccurate, the information after processing would be inaccurate,
therefore data should always be accurate so that it can be considered of good quality
Relevance
Data must be relevant to its purpose, the user must find data that is not required and
remove it, so that after processing only data required would be present
Age
Information must be up to date, as old information might be irrelevant as information tends
to change as time goes on. If data is not up to data it can lead to inaccuracy
Level of detail
Information should have the right amount of detail, it is possible for it to have to much detail
making it hard to extract information, if there is less information than required it can lead to
an inconvenience when using it.
Completeness
Information must be complete and have all required information to be of good quality, if not
it cannot be used properly for a particular purpose.
, Encryption
Symmetric
A method of encryption that requires the use of the same private key to encrypt and decrypt
files. Both the Encryptor and recipient needs to have the key, therefore the key must be sent
with the file/or separately.
Asymmetric
A method of encryption that uses a public key to encrypt files and a private key to decrypt
files. The Encryptor encrypts using a public key that is available to everyone and sends the
files to the recipient who decrypts using a private key known only to him/her.
Encryption protocols
Purpose of SSL/TLS
Enable Encryption in order to protect data
Make Sure the exchanging of data is from legit individuals who they say they are
Ensure data is not altered or corrupted while being exchanged
Use of SSL/TLS
Used in Web server to client communication, to establish a secure connection between both
parties, by helping both parties to agree on rules of communication by carrying through a
handshake protocol.
Uses of Encryption
Hard Disks
When a file is created/written on a disk, it is automatically encrypted, when it is read, it is
automatically decrypted while leaving other files encrypted.
The whole disk is encrypted so that data is protected if the disk is stolen or left unattended
Keys need to be secured in a well available location as data can’t be recovered without the
key
Data can be permanently lost if the encrypted disk crashes or the OS gets corrupted.
Email Encryption uses Asymmetric encryption, both the sender and Recipient exchange
messages between each other to add each other’s digital certificates, these are used to
encrypted files specific to each other to be decrypted.
Encrypting an email would encrypt any attachments
Emails are very susceptible to being intercepted by hackers, therefore encrypting all emails
are a good practice.
HTTPS
Hypertext transfer protocol is shown by a URL having HTTPS://, or a Padlock
A session key is encrypted using a public key which is sent to the webserver by a web
browser, then is decrypted using the servers private key, after which all exchange of
information is conducted using encryption using the session key.
HTTPS uses Asymmetric encryption initially to establish a secure session, then uses
symmetric encryption after that point forward.
After the session has ended, the symmetric key is disposed of.
, Slower than HTTP, needs to be kept up to date by the host, but is more secure in data
transfer and Sites with HTTPS is Ranked Higher/Given more priority by Search engines.
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