---
title: 1.7 Constants (const)
description: "A constant is an object whose value cannot be modified after it has been initialized. In C++, the `const` keyword is used to declare read-only variables. This example demonstrates how to declare a constant and use it in a program.…"
url: "https://edcret.in/docs/cpp-programming/basic-refreshers-cplusplus/1-7-constants-const/"
updated: "2026-07-28"
category: C++ Programming / Basic Refreshers
---

# 1.7 Constants (const)

A constant is an object whose value cannot be modified after it has been initialized. In C++, the `const` keyword is used to declare read-only variables.

This example demonstrates how to declare a constant and use it in a program.

## Source Code

```
#include <iostream>

int main()
{
    const float PI = 3.14159f;

    std::cout << "Value of PI: " << PI << 'n';

    return 0;
}
```

## Output

```
Value of PI: 3.14159
```

## Explanation

- `const float PI = 3.14159f;` declares a constant named `PI` and initializes it with the value `3.14159`.
- The `const` keyword makes the object read-only. Its value cannot be changed after initialization.
- A `const` object must be initialized when it is declared.
- Constant names are commonly written in uppercase to distinguish them from regular variables. This is a naming convention and is not enforced by the language.
- `std::cout << "Value of PI: " << PI << 'n';` prints the value stored in the constant.
- `return 0;` terminates the program successfully.