C Variables

What Is a Variable?

A variable in C stores a value in memory.

It must be declared with a data type before it's used.

Declaring and Initializing Variables

You can declare and assign a variable in one line or separately:

Common Data Types

C supports different types of variables. Here are three common ones:

• int: integers
• float: decimal numbers
• char: characters

Multiple Declarations

You can declare multiple variables of the same type on a single line:

Constants

Use const to create a variable whose value cannot change:

Naming Rules

Variable names:

• Must start with a letter or underscore
• Are case-sensitive (total ≠ Total)
• Cannot be a C keyword like int or return

Format Specifiers

Format specifiers tell printf() how to display the variable:

• %d – integer
• %f – float
• %.2f – float with 2 decimal places
• %c – character

Practice Question

Which of the following is invalid? Ask the AI chatbot to see if your answer is correct.

A. int speed = 100;

B. const float pi = 3.14;

C. int 1stPlace = 5;

Hint: Variable names can’t begin with a number.

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