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Parameters

Explore how to use parameters in C++ functions to pass data correctly and safely. Understand default parameters to simplify function calls and learn scope rules to manage variable access. This lesson helps you write error-free function calls and understand parameter passing essential for effective C++ programming.

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Parameters syntax

Parameters are how data is passed between functions through the call of the function.

We learned earlier that we list the data we want to pass to a function in the call between the ( ). The order of the list is determined by the function definition. The first parameter in the list will be assigned to the variable listed first in the function definition.

Note: In most cases, we must have the correct number and type of data being passed to the function, or we will receive an error when you try to compile your program.

Let’s look at an example below:

C++
#include <iostream>
using namespace std;
int fctn(int arg1, int arg2);
int main()
{
   int answer;
   int num1 = 10;
   answer = fctn(num1, 12);    // num1 and 12 are arguments passed to fctn
   cout << "Answer is: " << answer << endl;
}
int fctn(int arg1, int arg2)    // function definition
{
  cout << "num1 is assigned to arg1, value of arg1 is: "<<arg1<<endl;
  cout << "12 is assigned to arg2, value of arg2 is: "<<arg2<<endl;
  return arg1*arg2;      // mutliplying arg1 and arg2 and returning the answer
}

As you can see above, the contents of the variable num1 are passed to arg1 and the integer value 12 is ...