Summary
Summary AS2 Digital Technology Revision notes
- Module
- Digital technology
- Institution
- GCSE
AS2 Digital Technology Revision notes Including specification points
[Show more]
Seller
Follow
Content preview
Unit AS 2: Fundamentals of DigitalTechnology
https://quizlet.com/gb/458867469/ccea-digital-technology-as-2-flash-cards/?funnelUUID=d35c4c49-16ba-40f4-
98b2-6e69dcf81781
Data representation
Bits and bytes
• explain the terms bit, byte, kilobyte, megabyte, gigabyte and terabyte;
Bit - A Binary digIT. The smallest unit of data stored by a computer. Represented by a 0 or 1
Byte - A group of 8 bits in a character.
Kilobyte - 1024 bytes = 210 bytes
Megabyte - 1024 kilobytes = 220 bytes
Gigabyte - 1024 megabytes = 230 bytes
Terabyte - 1024 gigabytes = 240 bytes
• demonstrate that 2n different values can be represented with n bits (maximum n = 8);
28 27 26 25 24 23 22 21 20
256 128 64 32 16 8 4 2 1
Binary and decimal
• perform conversions from decimal to binary and from binary to decimal for a maximum of 8 bits;
• demonstrate how the two’s complement system can represent positive and negative numbers in
binary using 8 bits;
- The most significant bit (MSB) is used as a sign bit.
- If it is 0 the number is positive. If it is 1 the number is negative.
- For a positive number place values are used.
- Twos complement:
1. invert the bits of its positive equivalent
2. and add 1 to the least significant bit (LSB).
3. The most significant bit (MSB) is used as a sign bit.
• demonstrate how American Standard Code for Information Interchange (ASCII) and Unicode are
used to represent characters;
Character set
- A range of characters and symbols that can be represented by a unique binary code for each
, character.
- These include displayable characters, digits, punctuation and control codes.
American Standard Code for Information Interchange (ASCII)
- A character set that had a 7-bit set of codes that allow 128 different characters.
- 96 displayable characters and 32 control codes.
- Only used in the English language
- An 8th bit can be used as a parity bit for error checking.
- 8 bits can be used to represent 256 characters and control codes: Extended ASCII.
Unicode
- Uses 16 to 32 bits to represent 65536 characters.
- For most languages from around the world.
- May take up more storage space.
- Can take longer to process.
Data and information
Data, information and knowledge
• distinguish between data, information and knowledge by using examples;
Data
- Raw facts and figures with no meaning.
Information
- processed data that has meaning.
Knowledge
- The result of applying rules to information to assist decision making.
• describe how the quality of the information produced can be affected by the following factors:
- Accuracy, relevance, up to date/currency, completeness, presentation and reliability.
Up to date
- If you are asked to attach a photograph of yourself to your university application and you
upload a photo of you on your 8th birthday, is this up to date?
Relevance
- Data must be relevant for its intended purpose
Completeness
- You get a phonecall from Next about coming for an interview for a part time job. You thank
them and they end the call. They did not give you the date, time or location of the interview.
The information in incomplete
Reliability
- You are due to start University of Ulster next September and you ask for the start date. A
, person who just started Queen's tells you that you start on the 5th September. Is this
information from a reliable source?
Accuracy
- Data does not have to be 100% accurate but it should be accurate enough for the purpose.
Presentation
- When a house is being advertised for sale pictures are included in the brochure to make it
easier to decide
ARCPUR
Data validation and verification
• describe and apply the following data validation methods:
- range, type, length, format, presence, Modulus 11 check digit and lookup;
Range check
- Ensures that data is within a lower and upper limit.
Type check
- Checking that data value is of the correct type e.g. text, numeric, Boolean, Date/Time
Length check
- Checks that the data value contains a certain number of characters.
Format check
- Ensures that data matches a predefined pattern.
Presence check
- Data must be entered as it is mandatory.
Lookup
- Data value entered is compared against a predefined list of data values which the computer
will find a match.
Modulus 11 check digits
- AN EXTRA DIGIT ADDED AS PART OF A NUMBERIC DATA ITEM
- If the remainder is 0 there is a result of 11 so the check digit is 0
- If the remainder is 1 there is a result of 10 so the check digit is X
• understand the purpose of the following data validation methods:
- check digits; and
- batch totals (hash and controls);
How effective is the check digit at detecting transposition errors?
- A check digit can detect most transposition errors
- TRANSPOSITION ERROR: where two adjacent characters are switched.
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller mdhokia528. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for £8.16. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
52510 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy revision notes and other study material for 14 years now