Defensive Design Considerations:

Question 1

What are the different checks?

Answer 1

• Type Check.
• Pressence Check.
• Range.
• Format.
• ## Length.

Question 2

What is input validation?

Answer 2

• Checking data inputted by the user.

- Meets specific criteria + rules before processing.

Question 3

What is a type check?

Answer 3

• Checks whether it is the correct data type.
• E.g:
• Integer.
• Strings.
• Real.

Question 4

What is a range check?

Answer 4

• Checks whether the data is entered in the correct range.

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Question 5

What is presence check?

Answer 5

• Checks if data has been entered or in required fields.

Question 6

What is a format check?

Answer 6

• Checks if the format is correct.
• E.g: Days, months years.
• Postcode.

Question 7

What is a length check?

Answer 7

• Checks if it is the specific number of characters or over the specific minimun number of chaarcters.

Question 8

What are the advantages of validation?

Answer 8

• More robust.
• User friendly.
• Prevents errors.

Question 9

What errors can occur in a programme?

Answer 9

• Division by 0.
• Communication.
• Printer + Peripheral error.
• Disk errors.

Question 10

What is division by 0 error?

Answer 10

• No number when multiplied or divided by 0 will output a value/number.
• Make sure the code is dividing a number not by 0.

Question 11

What is a communication error?

Answer 11

• Online systems require connection to host servers.
• If server drops could cause programme to crash.
• Programmer should enable ways for the user to cancel requests + fail gracefully + reporting the connection error.
• Programme can automatically resume when connection is avaliable again.

Question 12

What is a printer and peripheral error?

Answer 12

• When a Programme outputs a hardcopy, printer could run out of ink and paper, jam.
• Programmer should not assume:
• Output to printer was sucessful.
• Should always have options to reprint reports and receipts.

Question 13

What is a disk error?

Answer 13

• Programs that read and write to files need to handle many types of exceptions:
  e. g:
• file/folder not found.
• disk being run out of space.
• data in file being corrupted.
• robust programmes handles this:
• Checks files + data before attempting to use them for further processing.