C++ Day 3

Great! Welcome to Day 3 of learning C++. Today, we will explore fundamental parameter passing, scope, and functions. Writing modular, reusable, clean code depends on these fundamental ideas.

C++ Day 3: Scope and Functions
1. What is a Function?
A task done by a block of code known as a function is Functions help to divide a big program into more manageable parts.

2. Function Syntax
return_type function_name(parameter1, parameter2, . . . ) {
// Code to run
value return; // if return_type is not void
{
✅ Example:
int add(int a, int b)
return a + b;
}

int main
std::cout << add(5, 3); // Output: 8
return 0.
}}
Three kinds of functions:
Void functions lack return value.

Return-type functions: Give back a value.

Parameterless functions: No input

Parameterized functions: Accept input

four. Definition versus Declarations of Function
Prototype declaration:

Tells the compiler a function exist: int multiple(int, int);
Definition:

int multiply(int x, int y) {
return x * y;
}
Scope in C++ five.
Scope is the area of a program wherein a variable is created and accessible.

Inside a function or block, local scope

Global scope: outside all activities

Inside the function only: functional scope

Example:
int globalVar = 10;

void show() {
int local Variable = 5;
std::cout << globalVar; // good
std::cout << localVar; // OK
}

int main() {
std::cout << globalVar; // OK
// std::cout << localVar; Error
return 0;
}
6. Pass by Value versus Pass by Reference
Pass by Value:
The function copies the variable.

void square(int x) {
x = x times x;
}

int main()
int num = 5;
square ( num );
std::cout << num; // Output: 5
}
Passing by Reference:
The function receives a reference, therefore the original may be changed.

void square(int &x)
x = x times x;
}}

int main() {
int num = 5;
square(num);
std::cout << num; // Output: 25
]
✅ Summary for Day 3:
You discovered how to define and declare functions.

C++ let you investigate several different scopes.

You discovered by reference and by value how data is transmitted to functions.