Choosing a validation check for a field

Name:

Date:

Class:

Quick Questions

Shade in the A or B circle for each question.

1. A form asks for a student's age, which must be between 11 and 18. Which validation check is the best choice?

A Presence check

B Range check

2. A 4-digit PIN is being entered. Which pair of checks suits this field?

A Length check and type check

B Range check and format check

3. A user must not leave the Name field blank. Which check should you choose?

A Check digit

B Presence check

4. A postcode must follow a set pattern of letters and numbers, such as 'AB12 3CD'. Which check is best?

A Format check

B Range check

5. A shop scans ISBN numbers on books. Which check can detect a mistyped digit?

A Check digit

B Presence check

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1Age: range check (0 to 120)		ARecalculate the check digit and compare it
2Name: presence check		BLENGTH(PIN) = 4 AND PIN is all digits
3A PIN must be exactly 4 digits, so a length check and a type check are both needed		CA postcode is a pattern of letters and digits, so it needs a format check, not a range check.
4An ISBN or barcode can be checked for typing errors using its last digit, so a check digit is chosen		DA presence check only tests that something was entered, so 500 would still pass. Use a range check for age.
5Postcode field: use a range check (1 to 9999)		EAge is a number that must sit between a lowest and highest sensible value, so a range check is the best choice.
6Age field: use a presence check to make sure age is sensible		FA name must not be left empty, so a presence check is chosen to make sure something has been entered.

Definitions

validation check

Fill in the Blanks

Complete each line of code by filling in the missing parts.

// Age must be between 0 and 120 IF Age >= 0 ___ Age <= 120 THEN OUTPUT "Age accepted"

// PIN must have exactly 4 digits IF ______(PIN) <> 4 THEN OUTPUT "PIN must be 4 characters"

INPUT Name IF LENGTH(Name) = _ THEN OUTPUT "Name is required"

// Date of birth needs a ______ check

// ISBN: validate using a ___________

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A // Age field: range check

B INPUT Age

C WHILE Age < 0 AND Age > 120 DO

D OUTPUT "Enter 0 to 120"

E INPUT Age

F ENDWHILE

Question 2

A INPUT PIN

B WHILE PIN <> 4 DO

C OUTPUT "PIN must be 4 chars"

D INPUT PIN

E ENDWHILE

Question 3

A INPUT Name

B WHILE Name <> "" DO

C OUTPUT "Name is required"

D INPUT Name

E ENDWHILE

Question 4

A CASE OF Field

B "Age": Check ← "Range"

C "Name": Check ← "Presence"

D "Date": Check ← "Range"

E ENDCASE

Question 5

A Field ← "ISBN"

B Check ← "Presence check"

C Reason ← "Detects typos"

D OUTPUT Check, Reason

Answer Key

Choosing a validation check for a field

Section A: Quick Questions

B — Range check

A — Length check and type check

B — Presence check

A — Format check

A — Check digit

Section B: Match the Pairs

Age: range check (0 to 120) → Age is a number that must sit between a lowest and highest sensible value, so a range check is the best choice.

Name: presence check → A name must not be left empty, so a presence check is chosen to make sure something has been entered.

A PIN must be exactly 4 digits, so a length check and a type check are both needed → LENGTH(PIN) = 4 AND PIN is all digits

An ISBN or barcode can be checked for typing errors using its last digit, so a check digit is chosen → Recalculate the check digit and compare it

Postcode field: use a range check (1 to 9999) → A postcode is a pattern of letters and digits, so it needs a format check, not a range check.

Age field: use a presence check to make sure age is sensible → A presence check only tests that something was entered, so 500 would still pass. Use a range check for age.

Section C: Definitions

validation check — A test matched to the field: range for age, length and type for PIN, presence for name, format for dates or postcodes, check digit for ISBN. Always justify the choice.

Section D: Fill in the Blanks

// Age must be between 0 and 120
IF Age >= 0 AND Age <= 120 THEN
    OUTPUT "Age accepted"

// PIN must have exactly 4 digits
IF LENGTH(PIN) <> 4 THEN
    OUTPUT "PIN must be 4 characters"

INPUT Name
IF LENGTH(Name) = 0 THEN
    OUTPUT "Name is required"

// Date of birth needs a format check

// ISBN: validate using a check digit

Section E: Spot the Error

C — A range check on age rejects a value that is too low OR too high. No number is both below 0 and above 120, so AND never rejects anything. It should be OR.

B — A length check must count the characters with LENGTH(PIN). Comparing PIN itself with 4 tests the value, not how many characters it has. It should be WHILE LENGTH(PIN) <> 4 DO.

B — A presence check must repeat the question when the field is empty. Name <> "" repeats when something has been entered, which is backwards. It should be WHILE Name = "" DO.

D — A date has a fixed pattern such as DD/MM/YYYY, so a format check is the best fit. A range check suits numbers like age. The line should assign "Format".

B — An ISBN needs a check digit, which is calculated from the other digits and detects mistyped numbers. A presence check only tests that something was entered. It should be "Check digit".