CS 10 SI Classroom Session 3 - rand() and srand() example

randExample.cpp

#include <iostream>
#include <cstdlib>

using namespace std;

int main() {

  // test the rand() function a few times 
  cout << rand() << "\n"
       << rand() << "\n"
       << rand() << "\n" << endl;

  // rand() prints out a number between 0 and RAND_MAX
  cout << "RAND_MAX: " << RAND_MAX << endl << endl;

  // test the srand() function 
  srand(42);

  cout << "rand() seeded with 42:" << endl;
  cout << rand() << "\n"
       << rand() << "\n"
       << rand() << "\n" << endl;

  // using time() to generate a different seed every time 
  srand(time(NULL)); 

  cout << "rand() seeded with current time: " << endl;
  cout << rand() << "\n"
       << rand() << "\n"
       << rand() << "\n" << endl;
 
  // what range of numbers will be printed out by these statements?
  cout << "rand() % 10:" << endl;  
  cout << rand() % 10 << endl;

  cout << "rand() % 5:" << endl;  
  cout << rand() % 5 << endl;

  cout << "rand() % 2:" << endl;  
  cout << rand() % 2 << endl;



  cout << endl;
  cout << "rand() % 10 + 5:" << endl;  
  cout << rand() % 10 + 5 << endl;

  cout << "rand() % 10 + 5:" << endl;  
  cout << rand() % 10 + 5 << endl;

  cout << "rand() % 10 + 5:" << endl;  
  cout << rand() % 10 + 5 << endl;


  cout << endl;
  cout << "rand() % 7 + 1939:" << endl;  
  cout << rand() % 7 + 1939  << endl;

  cout << "rand() % 10 - 150:" << endl;  
  cout << rand() % 10 - 150 << endl;

  cout << "rand() % 1:" << endl;  
  cout << rand() % 1 << endl;

  return 0;
}