Variables and Datatypes

Variables

Data is stored in the memory.
However, if I want to store certain data in a data block, I'll need to name it so I can call it specifically. This is a variable.

So, a Variable is a named memory location.

Rules to Naming Variables

• Has to start with a letter or underscore (preferably don't start with underscore)
• After the first letter, you can use letters, numbers or underscores.
• No spaces.
• No keywords.

C++ variables are case sensitive, so age, Age and AGE are different.

DataTypes

Now, in this variable the kind of data we store is called a Datatype.
So, a DataType helps us specify the size and the type of data.

Types of DataTypes

There are 3 categories of datatypes:

• Built In / Primitive Datatypes
• Derived Datatypes (To be learnt in later stages)
• User Defined Datatypes (To be learnt in later stages)

Primitive Datatypes

The basic datatypes in use are:

1. int

Stores integer numbers.
Syntax as:

int num = 123;

2. float

Stores decimal numbers.
Needs to be suffixed with a f since c++ automatically treats it as a double.
Syntax as:

float num = 12.34f;

3. double

Stores higher precision decimal numbers.
Syntax as:

double num = 12.34567;

4. char

Stores characters.
Needs to be enclosed in single inverted commas ''.
Syntax as:

char ch = 'a';

5. bool

Stores true or false values.
Similarly, also a 1 represents true and 0 represents a false.
Syntax as:

bool isHere = false;
isHere = 0;
isHere = true;
isHere = 1;

6. void

This will be discussed with functions for more understanding.

Variation of int and double

There are further variations to integers as:

Type	What it means
short	Short integer
int	Regular integer
long	Long integer
long long	Longer integer (suffix LL)
unsigned int	Integer that cannot be negative

Type	What it means
float	Usually 32-bit precision (suffix f)
double	Usually 64-bit precision
long double	At least as much precision as double but can provide more (suffix L)