AS2 Flashcards
What is a character set
All of the characters that a specific computer system can represent. It includes - Letters - Digits - Symbols (#@£) - Special e.g. return, end of file
How are characters represented
Unique binary code used to represent each character
Explain what ASCII is
American Standard Code for Information Interchange
It has 7 bits for data +1 for error checking
ASCII extended uses 8 bit of data
Max of 128 257 characters 0-127
Not enough for all world language because it is based in American English
Explain what Unicode is
Stands for unified coding system It uses 8,16,32 but versions 256 or 16. 4 l or 4.3 billion characters First 256 are same as ASCII More unique code ...Lot more characters ... All world languages and more
Define Data
Data is raw facts and figures without context or meaning
Define Information
Information is data which has been processed in order to give context and meaning
Define Knowledge
Is the application of information
What are the six factors that affect the quality of information and explain them
Accuracy - The information is precise, correct i.e. it is the true value that it is meant to be.
Relevance - Is the data applicable our use in the given situation
Up-to-Date - Information can change quickly, so if it is not up to date you can trust or rely on it
Completeness - Are there any types of missing facts from the information
Presentation - The way the info is displayed can be difficult to use or understanding
Reliability - Is the information trustworthy? Lots of data comes from other sources. May not know how it was collected or quality controls used.
What is Validation
It helps ensure correctness of data, it is done by computer when data is entered
It doesn’t guarantee accuracy.
Correctness : Sensible, meets rules, within limits.
What is Presence Check
Cannot be left blank, data must be input. E.g. Persons name of form
What is Length Check
Right number of characters
e.g. phone number, stock code
What is Range Check
Number/Data within set limits. It mat only have 1 limit
e.g. exam score 0-100
Bank account £0 or bigger
What is Type Check
Data must be of a set type
e.g. Currency, date, letters, number
What is Format Check
Where input data is in a specified format
E.g. LLNNLLN for stock code
What is Format Check
Where input data is in a specified format
E.g. LLNNLLN for stock code
What is Look up check
Checks input value against a list of allowed values eg user name
What is Check Digit and how does it work
The original data is used to calculate a value.
This check digit is then applied to the original data.
When input: (How it works)
Computer will use original data minus check digit to perform same calculation.
Compare its calculated value to the input check digit
If they match, the input is accepted. If they don’t match, the input is rejected
Describe how a check digit would detect an input error
Calculation uses weights based on each digits position.
If wrong digit is in any position
Different result will be calculated.
….Error detected
What is Modulus 11 and how does it work
Like all check digits, a value is calculated from original data based on weights applied to position of digits in original data.
- Start on Right
- Weight each digit starting with 2, 3,4 etc.
- Multiply weight x digit
- Add up all of the product
- Divide the sum by 11 int and remainder
What happens when importing a batch of data
The inputs are grouped together into batches e.g. 100 meter reading
Calculate values from each batch manually.
Values are then input into system before the data
When all data input
-Computer recognises values from input
-Compares against original check values
- If match accept, else rejects all batch
What is the Hash Total
It has no significant meaning/importance
e.g. house numbers or readings
What is the Control Total
They have significance important
e.g. All the units of electricity used, Total value of all the orders
What is Verification
It is done by humans when importing data
It helps ensure accuracy
What are the different types of verification techniques
- Proof Reading
- Double Entry
- Computer compares 2 inputs which it rejects if don’t match
What are the limitations of Validation
Cannot ensure accuracy (only correctness)
e.g. a valid dob is not necessary the right DOB is
What are the limitations of Verification
Human error
explain the terms bit, byte, kilobyte, megabyte, gigabyte and terabyte
Bit = 1 or 0 Nibble = 4 bits Byte = 8 bits KB = 1024 bytes GB = 1024 kilobytes MB = 1024 gigabytes TB = 1024 megabytes
