Constants in C language

What is a Constant?

A constant is a value that cannot be changed once defined during program execution.

Types of Constants

• Integer constants — e.g. 10, -45
• Floating-point constants — e.g. 3.14, 0.5
• Character constants — e.g. 'A', '9'
• String constants — e.g. "Hello"

Declaring Constants in C

Two common ways to define constants:

#define PI 3.14159

const int MAX_AGE = 100;

#define vs const

• #define is handled by the preprocessor and does no type checking.
• const is a type-safe qualifier checked by the compiler.