LU7: Errors, Threats, and Security

Q1: What does GIGO stand for?

Garbage In, Garbage Out

what does GIGO mean

incorrect input produces incorrect output.

Q2: What are human input errors?

inputting data that is

• incorrect

• inaccurate

• invalid

• wrong type of data

what are the four sources of errors

1. human errors

2. arithmetic

3. data transmission

4. programming

List and explain the four different types of arithmetic errors (8)

1. Rounding: Accuracy is lost in decimal places when a number is rounded.

2. Truncation: Removing decimal values by cutting off a number, e.g. converting a decimal to an integer.

3. Fixed Number of Bits: available bits limit the highest and lowest numbers that can be stored. Numbers outside this range cannot be stored.

4. Overflow: When a calculation produces a result that exceeds the maximum value allowed for a data type, causing an incorrect answer. (still performed)

what are data transmission errors

• When Data doesn't reach its destination intact, And there is a risk of data corruption

What are three causes of data transmission errors? (6)

Atmospheric conditions: Excessive heat or moisture damages cables.

Distance limits: Signals weaken over long distances due to attenuation.

Interference-causing devices: Motors, fluorescent lights and nearby electrical cables interfere with signals, causing data loss or corruption.

What are programming errors?

Bugs in computer programs that can cause incorrect results or system failures.

List 3 solutions for errors

verification, validation, techniques for input

What is data verification?

Checking that data meets set standards for completeness, correctness and consistency, by evaluating performance

Give an example of verification.

Entering a password twice and checking that both entries match.

What is data validation?

Checking the accuracy and quality of inputted data

What happens if data fails validation? (2)

The user is asked to re-enter the data, or the program assigns a valid default value.

What are the different types of validation checks? (10)

1. Presence

2. range

3. uniqueness

4. length

5. format

6. logical

7. check digit

8. checksum

9. data transmission check (parity).

What is a presence check? Explain and give an example

A: Ensures that data has been entered.

- Example: An ID number must be entered.

What is a range check? give example.

A: Ensures that data falls within an allowed minimum and maximum.

- Example: The number of hours worked cannot exceed the allowed range.

What is a uniqueness check? example

A: Ensures that no duplicate data exists.

- Example: Each user must have a unique login name.

What is a length check? example.

A: Ensures that data contains the required number of characters.

- Example: A South African ID number must contain 13 digits.

What is a format check? example.

A: Ensures that data follows a required pattern or format.

- Example: A date must follow the correct date format.

what is a type check? example.

A: data must be of appropriate type

• Example: date and time must be of a DataTime type

What is a logical check? example

A: Ensures that data makes sense logically.

- Example: A delivery date cannot be earlier than the order date.

What is a check digit? example,

A: A digit calculated from other digits to help detect data-entry errors.

- Example: Used in ISBN numbers.

What is a checksum? example

A: A value calculated from data to check whether it has changed or become corrupted during transfer.

• Example: the CRC algorithm used in the trailer of a data packet

Q18: What is a data transmission check (parity)?

A: Adds an extra bit to data to help detect errors during transmission.

What is important in checks?

order of checks

presence check must be first

What is the difference between Validation and Verification? (6)

Validation

• Timing: typically occurs at the point of data entry

• Purpose: ensures input data meets criteria (data type, format, range)

• Methods: using input masks, drop down lists, error messages to alert user to rectify invalid entries

Verification

• Timing: occurs after data has been captured & stored in database

• Purpose: ensures accuracy & consistency (compares against og sources)

• Methods: cross referencing with source documents, performing checksums, conducting audits to check if data is correct

What are the 7 techniques for input?

1. keyboard input

2. barcode scanner

3. QR codes

4. Biometric input

5. ORC

6. RFID

7. GUI components

Why should alternative input methods be used instead of keyboards?

They can reduce typing errors

Therefore, must key in as little as possible.

The more data entered, the higher chance of errors.

Why is keyboard input less favourable? (2)

user is free to key in whatever from keyboard

more inputted data = more difficult to validate

What is a barcode scanner?

A: A device that reads a barcode to enter data automatically into a computer. (pointer to a record in a database)

How does a barcode scanner work in a shop?

A: It reads an item's barcode to retrieve its details and price from a database.

What are the advantages of barcode scanners?

• Faster and more accurate than manual typing.

• Can automatically update prices and apply discounts.

• Reduces the need for manual data entry.

What is a QR code?.

A: A two-dimensional barcode

What are the advantages and uses of QR codes over and above barcodes? (3)

• Can be scanned using a smartphone.

• Doesn’t require hardware & software like a barcode would

• Can link to websites, documents and URLs.

What are examples of GUI components?

• Menus

• Drop-down boxes

• Radio buttons

• Checkboxes