AS2

Question 1

What is a character set

Answer 1

All of the characters that a specific computer system can represent.
It includes 
- Letters
- Digits
- Symbols (#@£)
- Special e.g. return, end of file

Question 2

How are characters represented

Answer 2

Unique binary code used to represent each character

Question 3

Explain what ASCII is

Answer 3

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

Question 4

Explain what Unicode is

Answer 4

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

Question 5

Define Data

Answer 5

Data is raw facts and figures without context or meaning

Question 6

Define Information

Answer 6

Information is data which has been processed in order to give context and meaning

Question 7

Define Knowledge

Answer 7

Is the application of information

Question 8

What are the six factors that affect the quality of information and explain them

Answer 8

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.

Question 9

What is Validation

Answer 9

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.

Question 10

What is Presence Check

Answer 10

Cannot be left blank, data must be input. E.g. Persons name of form

Question 11

What is Length Check

Answer 11

Right number of characters

e.g. phone number, stock code

Question 12

What is Range Check

Answer 12

Number/Data within set limits. It mat only have 1 limit
e.g. exam score 0-100
Bank account £0 or bigger

Question 13

What is Type Check

Answer 13

Data must be of a set type

e.g. Currency, date, letters, number

Question 14

What is Format Check

Answer 14

Where input data is in a specified format

E.g. LLNNLLN for stock code

Question 15

What is Format Check

Answer 15

Where input data is in a specified format

E.g. LLNNLLN for stock code

Question 16

What is Look up check

Answer 16

Checks input value against a list of allowed values eg user name

Question 17

What is Check Digit and how does it work

Answer 17

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

Question 18

Describe how a check digit would detect an input error

Answer 18

Calculation uses weights based on each digits position.
If wrong digit is in any position
Different result will be calculated.
….Error detected

Question 19

What is Modulus 11 and how does it work

Answer 19

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

Question 20

What happens when importing a batch of data

Answer 20

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

Question 21

What is the Hash Total

Answer 21

It has no significant meaning/importance

e.g. house numbers or readings

Question 22

What is the Control Total

Answer 22

They have significance important

e.g. All the units of electricity used, Total value of all the orders

Question 23

What is Verification

Answer 23

It is done by humans when importing data

It helps ensure accuracy

Question 24

What are the different types of verification techniques

Answer 24

• Proof Reading
• Double Entry
• Computer compares 2 inputs which it rejects if don’t match

Question 25

What are the limitations of Validation

Answer 25

Cannot ensure accuracy (only correctness)

e.g. a valid dob is not necessary the right DOB is

Question 26

What are the limitations of Verification

Answer 26

Human error

Question 27

explain the terms bit, byte, kilobyte, megabyte, gigabyte and terabyte

Answer 27

Bit = 1 or 0 
Nibble = 4 bits
Byte = 8 bits
KB = 1024 bytes
GB = 1024 kilobytes
MB = 1024 gigabytes
TB = 1024 megabytes