3.2.1 Data Types

Data can consist of numbers, characters, symbols, logical data or images. Data can be
stored in many different forms called 'Data Types'. These forms determine what actions
can be performed on the data when it is assigned to a variable in programming, or a
field in a Database or Spreadsheet.

• All data, whether they be numbers, text, symbols, logical, images or video are stored as a series of binary digits, 1s and 0s which the computer needs to know how to interpret.
• In a computer program, a variable is used to hold data that can be used or manipulated in certain ways depending on the type of data it is assigned.
• Computers need to be told what type of data it is, so they know how it can be manipulated and represented.
• For Example:
  • A student creates a variable called FirstName to hold the letters of a person's first name and they declare this variable's data type as String. The computer will interpret the 1's and 0's as letters. Even if it is a number, it will not work in a mathematical equation because the data type is String.
  • The Integer 5 * 5 = 25 but the String '5' * 5 = '55555'
  • Similarly, a variable called length is declared as Integer data type, and can be multiplied by another variable like width to give the area of a shape.

• In some programming languages, like Python, variable data types do not need declaring at all. The program will assume the data type of a variable based on what is put in it.
• For example, if you write (a = 21) and (b = "George") - a will be stored as an integer (whole number) and b will be stored as a string (text).
• Although you do not have to declare variable data types, you still need to understand the different data types and how to work with them in the programs your write.

• The table below details some of the main data types you will use:

The five main data types you will need to understand and use are:

• Integer.
• Real (Float).
• Character.
• String.
• Boolean.

Integer - Is a whole number which can be either positive (0 or above) or negative
(under 0). Lets look at how this can be used in pseudocode and Python.

Real - Is any number (positive or negative) including decimal places.
In Python areal number is called a floating-point number or float for short.

Character - Is a single symbol such as a letter. Take the word “hello” this
could be defined as 5 single characters “h”, ”e”, “l”, “l”, and “o”.

String - Is a series of characters that are combined to make a single piece of data.
They are defined by adding speech marks around the value. However, in Python anything
that the user inputs is treated as a string text unless otherwise specified.

• Q1: In the example code above why is the data type not defined? Will this code work and why?

Boolean - Boolean values can have one of two values, usually True or False and cannot be left empty.

Casting - Casting is when you convert a variable value from one type to another. This is,
in Python, done with functions such as int() or float() or str().