Error: wrong data type or undeclared variable

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Date:

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Quick Questions

Shade in the A or B circle for each question.

1. Which line causes a data type error?

A DECLARE Age : INTEGER Age ← 16

B DECLARE Age : INTEGER Age ← "sixteen"

2. Which program uses a variable that was never declared?

A Score ← 10 OUTPUT Score

B DECLARE Score : INTEGER Score ← 10 OUTPUT Score

3. DECLARE Marks : ARRAY[1:5] OF INTEGER Which statement uses an index outside the bounds?

A Marks[5] ← 70

B Marks[6] ← 70

4. DECLARE Name : STRING Which assignment is a data type error?

A Name ← 42

B Name ← "Maya"

5. Which fix corrects this error? Total ← 0 (Total was never declared)

A Add DECLARE Total : INTEGER before the assignment

B Change ← to = in the assignment

Match the Pairs

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

Left column		Right column
1DECLARE Age : INTEGER Age ← "twelve"		AAn error if Total was never declared: the variable is used without a DECLARE statement
2Total ← Total + 5		BDECLARE Name : STRING Name ← "Ava"
3An array index outside the bounds is a data type error because that element does not exist		CA data type error: a STRING value is assigned to a variable declared as INTEGER
4A variable must be declared with a data type before a value is stored in it		DPrice is used without DECLARE. Fix: add DECLARE Price : REAL before assigning the value.
5DECLARE Count : INTEGER Count ← "ten"		EDECLARE Scores : ARRAY[1:5] OF INTEGER Scores[6] ← 10
6Price ← 4.50 OUTPUT Price		FA STRING is assigned to an INTEGER variable. Fix: store a whole number such as Count ← 10, or declare Count as STRING.

Definitions

Data type error

Fill in the Blanks

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

_______ Score : INTEGER Score ← 10

DECLARE Name : ______ Name ← "Ava"

DECLARE Marks : ARRAY[1:5] OF INTEGER Marks[_] ← 90

DECLARE Price : ____ Price ← 4.5

DECLARE Total : INTEGER Total ← 0 OUTPUT _____

Spot the Error

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

Question 1

A DECLARE Age : INTEGER

B DECLARE Name : STRING

C Name ← "Sam"

D Age ← "fifteen"

Question 2

A DECLARE Score : STRING

B Score ← 0

C Score ← Score + 10

D OUTPUT Score

Question 3

A DECLARE Total : INTEGER

B DECLARE Counter : INTEGER

C Count ← 3

D Total ← Count * 2

Question 4

A DECLARE Marks : ARRAY[1:5] OF INTEGER

B Marks[1] ← 70

C Marks[6] ← 85

D OUTPUT Marks[5]

Question 5

A DECLARE Passed : BOOLEAN

B DECLARE Mark : INTEGER

C Passed ← "yes"

D Mark ← 62

Answer Key

Error: wrong data type or undeclared variable

Section A: Quick Questions

B — DECLARE Age : INTEGER Age ← "sixteen"

A — Score ← 10 OUTPUT Score

B — Marks[6] ← 70

A — Name ← 42

A — Add DECLARE Total : INTEGER before the assignment

Section B: Match the Pairs

DECLARE Age : INTEGER Age ← "twelve" → A data type error: a STRING value is assigned to a variable declared as INTEGER

Total ← Total + 5 → An error if Total was never declared: the variable is used without a DECLARE statement

An array index outside the bounds is a data type error because that element does not exist → DECLARE Scores : ARRAY[1:5] OF INTEGER Scores[6] ← 10

A variable must be declared with a data type before a value is stored in it → DECLARE Name : STRING Name ← "Ava"

DECLARE Count : INTEGER Count ← "ten" → A STRING is assigned to an INTEGER variable. Fix: store a whole number such as Count ← 10, or declare Count as STRING.

Price ← 4.50 OUTPUT Price → Price is used without DECLARE. Fix: add DECLARE Price : REAL before assigning the value.

Section C: Definitions

Data type error — An error caused by using a value its data type does not allow (e.g. a STRING stored in an INTEGER, or an index outside the array) or by using a variable that was never DECLAREd.

Section D: Fill in the Blanks

DECLARE Score : INTEGER
Score ← 10

DECLARE Name : STRING
Name ← "Ava"

DECLARE Marks : ARRAY[1:5] OF INTEGER
Marks[5] ← 90

DECLARE Price : REAL
Price ← 4.5

DECLARE Total : INTEGER
Total ← 0
OUTPUT Total

Section E: Spot the Error

D — Age is declared as INTEGER, so it cannot store the STRING "fifteen". It should be Age ← 15.

A — Score is used for arithmetic and is given the number 0, so it must be an INTEGER. Declaring it as STRING makes these lines data type errors.

B — The program declares Counter but then uses Count, which was never declared. The line should be DECLARE Count : INTEGER.

C — The array only has indexes 1 to 5, so index 6 is outside the bounds. It should be Marks[5] ← 85.

C — A BOOLEAN variable can only store TRUE or FALSE, not the STRING "yes". It should be Passed ← TRUE.