Types and Objects

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In programming, a type is a classification of data. This classification tells the compiler how to store such data and also informs the programmer what operations can be done on the type.

If you start googling programming types, you’ll realise the above is a very simple explanation, each layer you dig down the more complicated it gets. But for starting out in programming this should be enough.

Let’s take a look at some common types plus other common objects. I could break them out, but I want to try and keep this simple.


Commonly shortened to int in programming languages, this is used to store whole numbers, e.g. 2, 1450, -6.


A double allows us to store a number with a floating point, aka as a decimal, e.g. 1.5 -5.6.

Short, Long, and float

(Adding these for completion, but I rarely use them.)
Short is using to store small numbers ranging from -32,768 to 32,767.
Long is used to store really big numbers.
A float is used to store decimal points like a double, but has less precision.
It’s important to know about them, but unless you are writing a very memory conscious application, int and double will always be fine.


Very simple - it stores true of false. Commonly used in Control Flows.


Is a type to store single characters, e.g ‘a’, ‘t’. Its max length is 16-bit.


A string is technically not a type, it’s an object. But I want to keep this simple.
A string is essentially a collection of chars.
An example of a string would be “Richard”.


An array is used to store a collection of the same type. So we can have an array of Strings or Ints, but not an array of Ints and Strings. You can think of a food shopping list as an array - its collection of food types.

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Richard Bradshaw


Software Tester, speaker and trainer at Friendly Testing. BossBoss at Ministry of Testing. Whiteboard Testing creator. Striving to improve the testing craft.