Arrays

Question 1

Why are arrays better at storing data than variables?

Answer 1

If you have lots of similar data you can store it in 1 array instead of multiple variables as each variable is inefficient.

Question 2

What is an array?

Answer 2

A data structure that can store a collection of data values under one name.

Question 3

What is each piece of data in an array called?

Answer 3

an element

Question 4

How can each element be assessed in an array?

Answer 4

using its position or index

Question 5

When are arrays most helpful?

Answer 5

When you have lots of related data that you want to store and it doesn’t make sense to use separate values.
e.g. the names of pupils in a class, marks in a test etc

Question 6

How are they similar to variables?

Answer 6

Some languages require you to declare arrays before you use them.

Question 7

What is a one-dimensional array like?

Answer 7

lists

Question 8

How does this array work?
array rowers[4]
rowers[0] = "Mark"
rowers[1]  = "Adam"
rowers[2] = "Shelly"
rowers[3] = "Tobias"

Answer 8

The first line creates the array “rowers” and makes it size 4 (contains only 4 elements). The other lines assign the strings (names) in their positions in the array: 0,1,2 and 3.

Question 9

How can you retrieve elements from an array?

Answer 9

Use the name of the array and element’s position. Positions are numbered always starting at 0.

Question 10

How to change the value of the elements?

Answer 10

Reassigning the array position to a different data value. The previous value will be removed completely.

Question 11

How can FOR loops improve arrays if you combine them?

Answer 11

More systematic way of accessing and changing all of the elements in an array. They can also be used to search for specific elements or make a similar change to lots of elements.

Question 12

What is a two-dimensional array?

Answer 12

A one-dimensional array where each element is also a one-dimensional array.

Question 13

How is the position of an element written in a two-dimensional array?

Answer 13

[a,b] or [a][b], where a represents the position of the one-dimensional list that the element is in and b represents its position within that one dimensional list.

Question 14

An example of a two-dimensional array:

Answer 14

trees = [[“oak”, “ash”], [“beech”, “cedar”], [“pine”, “elm”]]

Question 15

How do you change elements in a two-dimensional array?

Answer 15

The exact same as in a one-dimensional array.

Question 16

How can two-dimensional arrays be used to store information about a digital image?

Answer 16

• each pixel’s information stored as an element in an array
• programmers can manipulate the image using array commands
• e.g. changing the value of pixels, cutting rows and columns out of the image etc.