What can be the use of the rand() of C++

[Gaauge]

Hello, Everybody. I am learning the C++ language. So, I do not know much more about the C++ language. Up till now I have learned how to use the functions and what can be the use of the functions in any program. So, I would like to know about the rand() function of the C++ language. Also, tell me how to use the rand() function in the C++ language. Reply Me!!!

[Reegan]

The rand() function of the C++ language can be used to produced the random numbers. The rand() function can returns a pseudo-random integral number in the range of 0 to RAND_MAX. These random numbers can be generated by an algorithm. This an algorithm can uses a seed to produce the series. The following can be the syntax of the rand() function as :

int rand ( int );

[opaper]

The programming code listed below can demonstrates you about the rand() function of the C++ language :

#include <stdio.h>
#include <stdlib.h>
#include <time.h>
int main ()
{
  int iScrt, iGss;
  srand ( time(NULL) );
  iScrt = rand() % 10 + 1;
  do
 {
    printf ("Guess the number (1 to 10): ");
    scanf ("%d",&iGss);
    if (iScrt<iGss) puts ("The secret number is lower");
    else if (iScrt>iGss) puts ("The secret number is higher");
  } while (iScrt!=iGss);
  puts ("Congratulations!");
  return 0;
}

Output of the above code can be as follows :

Guess the number (1 to 10): 5
The secret number is higher
Guess the number (1 to 10): 8
The secret number is lower
Guess the number (1 to 10): 7
Congratulations!

In the above example, the random seed can be initialized to a value that can be representing the second in which the program can be executed. The time can be defined in the header file <ctime>. In this way to initialize the seed can be generally a good option for most of the random needs.

[Modifier]

A typical way to produce the numbers that can be pseudo-random in a specified range using rand() can be to use the modulo of the value that can be returned by the range span and can adds the initial value of the range :
( val % 100 ) can be in the range 0 - 99
( val % 100 + 1 ) can be in the range 1 - 100
( val % 30 + 1985 ) can be in the range 1985 - 2014

[MindSpace]

The rand() function can returns a pseudorandom integer between zero and RAND_MAX. For example as :

     rand( time(NULL) );
     for( j = 0; j < 10; j++ )
       printf( "Random number #%d: %d\n", j, rand() );

You have to noticed that Do not use the modulus sign to limit the random numbers generated. The randomness can be heavily reduced. Inspite of use this algorithm to produce a proper distribution of random numbers between the 0 and other number :

 int randomNumber(int h)
    {
       const float scl = rand()/float(RAND_MAX);
        return int(scl*h);
    }