What Is a Variable?

A variable is a name used to store a value in a program.
You can think of a variable as a label atau attached to some data. Or a container like a box containing an apple.
Instead of using the value directly every time, we give it a name so it can be reused.

Why Variables Exist

Variables make programs flexible.
With variables, a program can:

store information
reuse values
update values over time

Without variables, programs would be static and difficult to maintain.

A Simple Example

age = 20

In this example:

age is the variable name
20 is the value

Now the program can use age instead of writing 20 everywhere.

Variable Declaration and Variable Assignment

When working with variables, there are two main actions:

Variable Declaration

Declaring a variable means introducing its name to the program.

Variable Assignment

Assigning a variable means giving it a value.

In some languages, declaration and assignment happen at the same time. In others, they can be separate steps.

Examples

Python (combined)

count = 5

C (separated)

int count;
count = 5;

The idea is the same. Only the syntax is different.

Updating a Variable

The value of a variable can change while the program is running.

score = 10
score = 15

The variable score now holds the value 15, not 10.

This ability to change values is what makes variables powerful.

Variable Naming Rules

Most programming languages follow similar rules for naming variables:

A variable name must not start with a number
Numbers are allowed, but not at the beginning
Do not use reserved keywords of the language
Variable names are case-sensitive
- total and Total are different
For names with multiple words, common styles include:
- snake_case
- camelCase

Examples

# Valid
user_name
totalScore
count2

# Invalid
2count
user-name
print

Choosing Good Variable Names

Good variable names make code easier to understand.

Compare:

x = 30

and

age = 30

The second example clearly explains what the value represents.

In Short

A variable stores a value
A variable has a name and a value
The value of a variable can change
Clear variable names improve readability