C++ Function Parameters

C++ Function Parameters and Arguments

Information can be passed to functions as a parameter. Parameters act as variables inside the function.

They are specified after the function name, inside the parentheses. You can add as many parameters as you want, just separate them with a comma.

1. Parameters and Arguments

• Parameter: A variable listed inside the parentheses in the function definition.
• Argument: The actual value that is passed to the function when it is called.

#include <iostream>
#include <string>
using namespace std;

// Function with one parameter
void greetUser(string name) {
  cout << "Hello " << name << "!\n";
}
int main() {
  greetUser("Alice"); // "Alice" is the argument
  greetUser("Bob");   // "Bob" is the argument
  return 0;
}

2. Default Parameter Values

You can provide a default value for a parameter by using the equals sign (=). If you call the function without passing an argument, it will use the default value.

#include <iostream>
#include <string>
using namespace std;

void setCountry(string country = "USA") {
  cout << "I am from " << country << "\n";
}
int main() {
  setCountry("Canada"); // Outputs: I am from Canada
  setCountry();         // Outputs: I am from USA (uses default)
  return 0;
}

3. Multiple Parameters

You can pass multiple parameters to a function by separating them with commas. When calling the function, ensure you pass the arguments in the exact same order!

#include <iostream>
#include <string>
using namespace std;

void displayInfo(string name, int age) {
  cout << name << " is " << age << " years old.\n";
}
int main() {
  displayInfo("John", 25);
  displayInfo("Emma", 22);
  return 0;
}

4. The return Keyword

If you want the function to compute a value and give it back to you, use a return type (like int, double, etc.) instead of void, and use the return keyword inside the function.

#include <iostream>
using namespace std;

int addNumbers(int x, int y) {
  return x + y; // Returns the sum of x and y
}
int main() {
  int result = addNumbers(5, 3);
  cout << "The sum is: " << result << "\n";
  return 0;
}