Numbers in C++

Normally, when we work with Numbers, we use primitive data types such as int, short, long, float and double, etc. 

The number data types, their possible values and number ranges have been explained while discussing C++ Data Types.

Defining Numbers in C++:

#include <iostream>
using namespace std;
 
int main ()
{
   // number definition:
   short  s;
   int    i;
   long   l;
   float  f;
   double d;
   
   // number assignments;
   s = 10;      
   i = 1000;    
   l = 1000000; 
   f = 230.47;  
   d = 30949.374;
   
   // number printing;
   cout << "short  s :" << s << endl;
   cout << "int    i :" << i << endl;
   cout << "long   l :" << l << endl;
   cout << "float  f :" << f << endl;
   cout << "double d :" << d << endl;
 
   return 0;
}

When the above code is compiled and executed, it produces the following result:

short  s :10
int    i :1000
long   l :1000000
float  f :230.47
double d :30949.4



Random Numbers in C++:


There are many cases where you will wish to generate a random number. 

There are actually two functions you will need to know about random number generation. 

The first is rand(), this function will only return a pseudo random number. 

The way to fix this is to first call the srand() function.

Following is a simple example to generate few random numbers. 

This example makes use of time()function to get the number of seconds on your system time, to randomly seed the rand() function:
#include <iostream>
#include <ctime>
#include <cstdlib>

using namespace std;
 
int main ()
{
   int i,j;
 
   // set the seed
   srand( (unsigned)time( NULL ) );

   /* generate 10  random numbers. */
   for( i = 0; i < 10; i++ )
   {
      // generate actual random number
      j= rand();
      cout <<" Random Number : " << j << endl;
   }

   return 0;
}
When the above code is compiled and executed, it produces the following result
 Random Number : 1748144778
 Random Number : 630873888
 Random Number : 2134540646
 Random Number : 219404170
 Random Number : 902129458
 Random Number : 920445370
 Random Number : 1319072661
 Random Number : 257938873
 Random Number : 1256201101
 Random Number : 580322989