Storing last generated random number and using integers from other functions.

Projects Programming
1

First of all, I consider myself new to the Arduino environment, therefore I may oversee some basic things.
So, I got a function in which a random number is generated. Every time I press (a) button (1) the function is called and thereby a new number is generated. But when another button (3) is pressed, I would like to receive the last number generated in that first function to get it compared with the input which is set by pressing button 2. What's is the easiest way of doing this?

void BINARY() //which is called by button 1
{
  int random_number = random(0, 16);

  for (int i = 0; i < 4; i++)
  {
    if (bitRead(random_number, i) == 1)
    {
      digitalWrite(ledPin[i], LOW);
    }
    else
    {
      digitalWrite(ledPin[i], HIGH);
    }
  }

}

void GUESSING_THE_NUMBER() //which is called by button 2
{
//Here goes the code to set your guess
}

void COMPARE() //which is called by button 3
{
//I would like to compare input with the last random number generated
}
2

Before you generate a new random number save the previous one to a variable

3

UKHeliBob:
Before you generate a new random number save the previous one to a variable

But how do I do that? I don't know what you mean by 'saving'.

4 
int previous_random_number = random_number;
int random_number = random(0, 16);

NOTE : previous_random_number and random_number are declared in the BINARY function so their values are only valid in that function. Read up on variable scope if you don't know what that means