const in c++ is same as globle in python

Explanation of const in C++

In C++, the const keyword is used to declare a constant variable. A constant variable is one whose value cannot be modified once it is initialized.

Here are the steps to understand const in C++:

1. Declaration: To declare a constant variable, the const keyword is placed before the data type. For example:

cpp const int x = 5;

In this example, x is a constant of type int with an initial value of 5.

1. Initialization: The constant variable must be initialized at the time of declaration. Once initialized, its value cannot be changed. In the above example, x is initialized with the value 5.

2. Usage: Constant variables are typically used when you want to define a value that should not be modified throughout the program. They are especially useful in scenarios where you want to prevent accidental modifications to a variable.

3. Compile-time Constant: Constant variables are resolved at compile-time. This means that the value of a constant is determined and fixed during the compilation process, and it cannot be modified or re-assigned during the program's execution.

4. Benefits: Using const helps in writing more robust and maintainable code. It allows you to express your intention that a particular variable should not be modified, and the compiler enforces this restriction. It also helps in code optimization, as the compiler can make certain assumptions about the constant values.

5. Scope: The scope of a constant variable is determined by its declaration. It can be declared at different levels, such as global scope, function scope, or block scope.

6. Global scope: If a constant is declared outside any function, it becomes a global constant accessible throughout the program.

7. Function scope: If a constant is declared inside a function, it is accessible only within that function.

8. Block scope: If a constant is declared inside a block (within curly braces), it is accessible only within that block.

Here is an example that demonstrates the scope of a constant variable:

```cpp #include

const int globalConstant = 10;

void func() { const int localConstant = 5; std::cout << "Local constant: " << localConstant << std::endl; }

int main() { std::cout << "Global constant: " << globalConstant << std::endl; func(); return 0; } ```

In this example, globalConstant is a global constant accessible throughout the program. localConstant is a constant declared inside the func() function and is accessible only within that function.

Output:

Global constant: 10 Local constant: 5

Note that both constants have the same name, but they exist in different scopes.

1. Using const with Pointers: In C++, you can also use the const keyword with pointers to define constant pointers or pointers to constant values.

2. Constant pointer: A constant pointer is a pointer whose value (the memory address it holds) cannot be modified. However, the value stored at that memory address can be modified.

cpp int x = 10; int y = 20; int* const ptr = &x; // constant pointer to an int *ptr = 15; // valid, modifies the value at the memory address ptr = &y; // invalid, cannot modify the pointer itself

• Pointer to constant: A pointer to constant is a pointer that points to a constant value. The value at the memory address cannot be modified through the pointer.

cpp int x = 10; const int* ptr = &x; // pointer to a constant int *ptr = 15; // invalid, cannot modify the value through the pointer x = 15; // valid, can modify the value directly

In both cases, the const keyword is used to specify the restriction either on the pointer itself or on the value it points to.

These are the key points to understand the const keyword in C++. It is important to use const correctly to ensure the intended behavior and to write safe and efficient code.