Lower bound and upper bound

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Quick Questions

Shade in the A or B circle for each question.

1. In ARRAY[1:30], what is the lower bound?

A 30

B 1

2. In ARRAY[1:30], what is the upper bound?

A 30

B 1

3. Which shows the bounds written in the correct order?

A ARRAY[30:1]

B ARRAY[1:30]

4. The lower bound of an array is...

A the index of the first element

B the number of elements in the array

5. Which is the correct way to separate the bounds in an array declaration?

A ARRAY[1:30]

B ARRAY[1-30]

Match the Pairs

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

Left column		Right column
1ARRAY[1:30]		ADECLARE Marks : ARRAY[1:25] OF INTEGER
2ARRAY[0:9]		BThe bounds are written the wrong way round. The lower bound must come first and the upper bound second, as l:u, so it should be ARRAY[1:30].
3The lower bound is the index of the first element, written before the colon		CThe two bounds are separated by a comma instead of a colon. A 1D array needs l:u, so it should be ARRAY[1:20].
4The upper bound is the index of the last element, written after the colon		DAn array whose first element has index 1 (lower bound) and whose last element has index 30 (upper bound)
5DECLARE Scores : ARRAY[30:1] OF INTEGER		EThe lower bound is 0 and the upper bound is 9, so the indexes run 0, 1, 2 ... 9
6DECLARE Ages : ARRAY[1,20] OF INTEGER		FDECLARE Names : ARRAY[1:40] OF STRING

Definitions

ARRAY[1:30]

Fill in the Blanks

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

DECLARE Scores : ARRAY[_:30] OF INTEGER // 30 elements, first index is 1

DECLARE Names : ARRAY[1:__] OF STRING // the last element has index 30

DECLARE Temp : ARRAY[_:6] OF REAL // 7 elements, first index is zero

DECLARE Marks : ARRAY[1_30] OF INTEGER

DECLARE Scores : ARRAY[1:30] OF INTEGER FOR Index ← 1 TO __ NEXT Index

Spot the Error

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

Question 1

A // Bounds of ARRAY[1:30]

B lower ← 30

C upper ← 30

Question 2

A // Temp is ARRAY[1:7]

B Temp[1] ← 18

C Temp[7] ← 25

D OUTPUT Temp[8]

Question 3

A // Names is ARRAY[0:9]

B first ← 0

C last ← 10

Question 4

A // Prices holds 12 values

B // Declared as ARRAY[12:1]

C OUTPUT Prices[1]

Question 5

A // Pupils is ARRAY[1,30]

B FOR n ← 1 TO 30

C OUTPUT Pupils[n]

D NEXT n

Answer Key

Lower bound and upper bound

Section A: Quick Questions

B — 1

A — 30

B — ARRAY[1:30]

A — the index of the first element

A — ARRAY[1:30]

Section B: Match the Pairs

ARRAY[1:30] → An array whose first element has index 1 (lower bound) and whose last element has index 30 (upper bound)

ARRAY[0:9] → The lower bound is 0 and the upper bound is 9, so the indexes run 0, 1, 2 ... 9

The lower bound is the index of the first element, written before the colon → DECLARE Marks : ARRAY[1:25] OF INTEGER

The upper bound is the index of the last element, written after the colon → DECLARE Names : ARRAY[1:40] OF STRING

DECLARE Scores : ARRAY[30:1] OF INTEGER → The bounds are written the wrong way round. The lower bound must come first and the upper bound second, as l:u, so it should be ARRAY[1:30].

DECLARE Ages : ARRAY[1,20] OF INTEGER → The two bounds are separated by a comma instead of a colon. A 1D array needs l:u, so it should be ARRAY[1:20].

Section C: Definitions

ARRAY[1:30] — In ARRAY[l:u], l is the lower bound (index of the first element) and u is the upper bound (index of the last). Here the lower bound is 1 and the upper bound is 30.

Section D: Fill in the Blanks

DECLARE Scores : ARRAY[1:30] OF INTEGER
// 30 elements, first index is 1

DECLARE Names : ARRAY[1:30] OF STRING
// the last element has index 30

DECLARE Temp : ARRAY[0:6] OF REAL
// 7 elements, first index is zero

DECLARE Marks : ARRAY[1:30] OF INTEGER

DECLARE Scores : ARRAY[1:30] OF INTEGER
FOR Index ← 1 TO 30
NEXT Index

Section E: Spot the Error

B — In ARRAY[1:30] the lower bound is the index of the first element, which is 1. It should be lower ← 1. The value 30 is the upper bound.

D — The upper bound of ARRAY[1:7] is 7, so the last valid index is 7. Temp[8] is outside the bounds. It should be OUTPUT Temp[7].

C — In ARRAY[0:9] the upper bound is 9, which is the index of the last element. It should be last ← 9. Index 10 does not exist.

B — Bounds are written lower:upper, so the lower bound comes first. It should be ARRAY[1:12]. The lower bound cannot be larger than the upper bound.

A — The lower and upper bounds are separated by a colon, written l:u. It should be ARRAY[1:30]. A comma is used to separate the dimensions of a 2D array.