The use of Variables, Constants, Inputs, Outputs & Assignments

Question 1

Define variable

Answer 1

A variable is a value stored in memory that can change while the program is running

Question 2

Define constant

Answer 2

A constant is a value that does not change while the program is running, and is assigned when the program is designed

Question 3

Define assignment

Answer 3

Assignment - Giving a variable or constant a value

Question 4

Define casting

Answer 4

Casting - Converting a variable from one data type to another

Question 5

Give an example of casting

Answer 5

For example, integer to string.

Question 6

What data types can a variable be

Answer 6

A variable can be an integer, character, string, real (float) or Boolean.

Question 7

Define input

Answer 7

Input - A value is read from an input device
e.g. keyboard

Question 8

Define output

Answer 8

Ouput - Data generated by the computer and displayed to the user.

Question 9

State the advantages of constants over variables

Answer 9

Constants make a program easier to read as they are usually declared and assigned at the top of the program

Constants can easily be changed by the programmer in one place in a program .
Instead of changing every instance of a value throughout a program.
This leads to less chance of errors

The complier can optimise the code.
This makes a program run more quickly if constants are used instead of variables.

Question 10

Why is casting needed

Answer 10

Casting is needed because:

Inputs from the keyboard are always characters. Multiple characters are called a string.
However to perform an addition, the Arithmetic Logic Unit (ALU) must use numbers.
Therefore a string has to be “cast” to a number

Integers require less bits of memory than numbers with a decimal part (real numbers)
Therefore it makes sense to use integers where we can to make a program more memory efficient.
However, it may be necessary to cast an integer to a real in a program.

Some commands also require data in a particular data type

Question 11

What is an integer

Answer 11

An integer is a whole number
(positive or negative)

Question 12

When would you use and not use integers

Answer 12

Use: total = total + score

Never use for telephone numbers

Use only when arithmetic on the data is required

Question 13

Give an example when an integer would be used in a piece of code

Answer 13

Integer
Use: total = total + score

Question 14

What is a real

Answer 14

A real is a number with a decimal part

Question 15

What is a real also called

Answer 15

Real also called a float (floating point number

Question 16

Example of an real

Answer 16

6.5

Question 17

Give an example when an real would be used in a piece of code

Answer 17

Real
Use: cost = total + vat

Question 18

What is a character

Answer 18

A character is a single alphanumeric

Question 19

Give an example of a character

Answer 19

Character
E.g. “1” or “a” (“1” on the keyboard pressed would be the character “1” not the number “1”)

Question 20

Give an example of code where a character would be used

Answer 20

Character -
Use: choice = input(“Enter your choice”)

Question 21

What is a string

Answer 21

A string is multiple alphanumeric characters

Question 22

What do you use string for

Answer 22

Strings are used for words and telephone numbers

Question 23

Give an example of a string
Give an example of when a string would be used in a piece of code

Answer 23

String

E.g. “Craig”

Use: forename = “Craig”