Pass-by-Value
In the pass-by-value approach, the function receives a copy of the argument, and any changes made to the parameter inside the function do not affect the original argument.
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#include <iostream> using namespace std; // Function to check if a number is prime or composite (pass-by-value) bool isPrime(int num) { if (num <= 1) return false; // Numbers less than or equal to 1 are not prime for (int i = 2; i <= num / 2; ++i) { if (num % i == 0) return false; // Number is divisible by i, so it's not prime } return true; // Number is prime } int main() { int number; cout << "Enter a number: "; cin >> number; if (isPrime(number)) { cout << number << " is a prime number." << endl; } else { cout << number << " is a composite number." << endl; } return 0; } |
Pass-by-Reference
In the pass-by-reference approach, the function receives a reference to the argument, allowing modifications to the argument inside the function to affect the original variable.
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#include <iostream> using namespace std; // Function to check if a number is prime or composite (pass-by-reference) bool isPrime(int& num) { if (num <= 1) return false; // Numbers less than or equal to 1 are not prime for (int i = 2; i <= num / 2; ++i) { if (num % i == 0) return false; // Number is divisible by i, so it's not prime } return true; // Number is prime } int main() { int number; cout << "Enter a number: "; cin >> number; if (isPrime(number)) { cout << number << " is a prime number." << endl; } else { cout << number << " is a composite number." << endl; } return 0; } |
Explanation
- Pass-by-Value: The
isPrimefunction receives a copy ofnumber. It performs the prime-checking logic on this copy. The original variable inmainremains unaffected by changes withinisPrime. - Pass-by-Reference: The
isPrimefunction receives a reference tonumber. Although the logic is the same as in the pass-by-value version, here it operates directly on the original variable. Any changes tonumwithinisPrimewould reflect inmain, but in this case, there are no modifications tonum.
Sample Output
Assuming you enter 7 as the number:
For Pass-by-Value:
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Enter a number: 7 7 is a prime number. |
For Pass-by-Reference:
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Enter a number: 7 7 is a prime number. |