C++ Program:

Example:

#include <iostream>
using namespace std;

int main() {
  int num;
  cout<<"Enter your last number: ";
  cin>>num;
  cout<<"Your even numbers are : ";
  for (int i=1; i<num; i++)
    if(i%2==0) cout<<i<<" ";
  return 0;
}

Output:

  Enter your last number : 7
  Your even numbers are : 2 4 6

You should know first :

Even numbers: Numbers perfectly divisible by 2

(number % 2 == 0)

So, we are using a for loop till the last number entered and check every value for even

for(int i=0; i<LastValue; i++) {
  //Check every 'i' for even, if even then print
}