Random Numbers in C++

To generate random numbers in C++ using the rand() function do the following:

Include the header file stdlib.h.
Once before you use rand you need to "seed" the random number generator using the srand function. There are two ways you can do this:
1. Ask the user for a seed (which is an unsigned integer), then call srand with the that seed as a parameter. The code is as follows:
```
       unsigned seed;
 
       cout << "Enter a seed for the random number generator: ";
       cin >> seed;
       srand (seed);
```
2. Seed the random number generator with the system time. For this method you need to include the header file time.h. The code is as follows:
```
       srand(unsigned (time ( (time_t *) NULL) ) );
```

Whenever you need a random number, call the function rand(), which returns an integer between 0 and RAND_MAX (a big number!). You can use modular arithmetic to get a number in whatever range you want. Some examples,

          x = rand();         // an integer between 0 and RAND_MAX
          x = rand() % 1000;  // an integer between 0 and 999
          x = 5 + rand() % 10; // an integer between 5 and 14
          y = rand()/ (double) rand(); // a real number

The C++ Library has other classes for random number generation. You are welcome to use any of them.