C++ Functions: Complete Guide & Usage

C++ functions are reusable blocks of code that can take input parameters, perform a specific task, and optionally return a value. They are an important concept in object-oriented programming that can improve code readability, maintainability, and reusability.

Here is the general usage of a C++ function:

1. Function definition: In C++, a function’s definition consists of the return type, function name, parameter list, and function body. For example:

int add(int a, int b) {
    return a + b;
}

1. Function call: calling a function by its name and providing a list of arguments, and using its return value (if any). For example:

int result = add(3, 4);

1. Function parameters: Functions can accept zero or multiple parameters to pass values to the function body for operations. Parameters can have different types, such as integers, floating point numbers, characters, etc. For example:

void printSquare(int num) {
    int square = num * num;
    cout << "The square of " << num << " is " << square << endl;
}

1. Function return value: A function can return a value to the place where it was called, allowing the caller to access the result of the function’s execution. The type of the return value must match the return type defined when the function was created. For example:

int multiply(int a, int b) {
    return a * b;
}

1. Function overloading is supported in C++, which means defining multiple functions with the same name but different parameter lists within the same scope. Different function overloads can be distinguished by the type, number, or order of the function parameters. For example:

int add(int a, int b) {
    return a + b;
}

double add(double a, double b) {
    return a + b;
}

1. Default parameters: In C++, functions can be set up with default parameters, meaning that when defining a function, certain parameters can be given default values. If these parameters are omitted when calling the function, the default values will be used instead. For example:

void printInfo(string name, int age = 0) {
    cout << "Name: " << name << endl;
    cout << "Age: " << age << endl;
}

The above is the basic usage of C++ functions, which can achieve various functions and logic through features such as function definition, invocation, parameters, return values, overloading, and default parameters.