help with rand function

[crimes]

Hey all, I'm creating a text-based RPG and am just now getting to the fighting mechanics. I want to use the rand function to choose a random number within a certain range but am having trouble getting it to execute correctly.

#include <cstdio>
#include <cstdlib>
#include <iostream>
using namespace std;

void fight();

int main()
{
fight();
}

void fight()
{
     int ap=10;
     int def=10; 
     int eap=5;
     int edef=5;   
     int dmg;
     int edmg;
     
         system("pause");
     
     dmg=(rand() % ap+1) + (def/edef);    //random number for dmg from 1 to ap 
     edmg=(rand() % ap+1) + (edef/def);  //random number for enemy damage from 1 to eap    
     cout<<"\n\nYou did "<<dmg<<" DAMAGE to the alien"<<endl;
     cout<<"\n the alien did "<<edmg<<" to you"<<endl;
     
     system("pause");
     
return;
     }

As you can see I put variables into my rand function. Is this even allowed? I wasn't sure so I tried anway. I want to have the dmg = a random number from 1 to their attack power(ap), plus the result of their defense divided by their opponents defense. I know something is wrong because when I run this piece it always gives me the same output. To temporarily solve it I could change the rand function to just say 10+1 but then when their attack power changes in the future its not going to be accurate. Thanks for anyone willing to help me out.

[Narue]

This may be helpful. I think the real problem here is you're not seeding rand properly and expecting the default seed to be different each time (which it's not).

[crimes]

thank you narue for the link. it was helpful