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++:

We already defined numbers in various example given in previous chapters. Here is another consolidated example to define various types of numbers of C++.

/*Defining Numbers: InfoBrother:*/
 
#include<iostream>
using namespace std;
 
main()
{
        //Numbers defining:
	short s;
	int i;
	long l;
	float f;
	double d;
 
	//assigning numbers;
	s=10;
	i=100;
	l=100000;
	f=25.5;
	d=2455.52;
 
	//display result:
        cout<<" short :" <<s<<endl;
        cout<<" int :" <<i<<endl;
        cout<<" long :" <<l<<endl;
        cout<<" float :" <<f<<endl;
        cout<<" double :"<<d<<endl;
 
        return 0;
}

 short 	:10
 int 	:100
 long 	:100000
 float 	:25.5
 double :2455.52

Math Operation in C++:

In addition to the various functions we can create, C++ also includes some useful functions we can use. these functions are available in Standard C and C++ libraries and called built-in functions. These are functions that can be include in our program and then use.

C++ has rich set of mathematical operations, which can be performed on various numbers. following table lists down some useful built-in mathematical functions available in C++.

/*<math.h> Operation: InfoBrother:*/
 
#include<iostream>
#include<math.h> //required for math operations:
using namespace std;
 
main()
{
    //Number Definition:
    short s=10;
    int i=-100;
    long l=10000;
    float f=230.52;
    double d=200.332;
 
    //Mathematical Operations:
    cout<<"sin(d):   "<<sin(d)	 <<endl;
    cout<<"cos(d):   "<<cos(d)	 <<endl;
    cout<<"acos(d):  "<<acos(d)	 <<endl;
    cout<<"abs(i):   "<<abs(i)	 <<endl;
    cout<<"floor(d): "<<floor(d) <<endl;
    cout<<"sqrt(f):  "<<sqrt(f)	 <<endl;
    cout<<"pow(d,2): "<<pow(d,2) <<endl;
    cout<<"cosh(d):  "<<cosh(d)	 <<endl;
    cout<<"exp(d):   "<<exp(d)	 <<endl;
    cout<<"log(d):   "<<log(d)	 <<endl;
    cout<<"trunc(d): "<<trunc(d) <<endl;
    cout<<"rint(d):  "<<rint(d)	 <<endl; 
 
    return 0;
}

sin(d)	:-0.666817
cos(d)	:0.745221
acos(d)	:nan
abs(i)	:100
floor(d):200
sqrt(f)	:15.1829
pow(d,2):40132.9
cosh(d)	:5.03561e+086
exp(d)	:1.00712e+087
log(d)	:5.29998
trunc(d):200
rint(d)	:200

Random Numbers In C++:

There are many cases where we wish to generate a random number. There are actually two function we will need to knwo about random number generation. The first is rand(), This function will only return a pseudo random number in the range from 0.0 to 32,767. The maximum value is Library-dependent, but is guaranteed to be at least 32767 on any standard library implementation. we can check it from RAND_MAX.

#include <iostream>
#include <cstdlib> //required for rand() function:
using namespace std;
 
main()
{
    int i = 0;
    while(i++ < 10) 
    {
        int r = (rand() % 100) + 1;
        cout << r <<" | ";
    }
 
    return 0;
}

However, the Numbers generated by the rand() are not rendom because it generates the sam sequence each time the code executed. so, if we run the code again and again, we'll get the same sequence repeated as in the previous run. To make a different sequence of numbers, we should specify a Seed as argument to a srand() function as shown in the given example.

srand(54545);

We will get the different sequence of numbers by using the srand() , however, the sequence will still be repeated each time the code is executed. To generate a ever changing sequence , we need to feed something other than static integer to the argument of the strand() function.

The best solution is to seed the rand() function using the current time as the argument to srand(), by calling time() function from the standard C++ library, < ctime > , then, for portability, we cast an integer type:

srand((int) time(0));

The time() function returns the number of seconds since 00:00 hours, jan 1, 1970 UTC ( i.e. current Unix time stamp ). this ensures the number generated by rand() will now seems to be truly random unless it is called again within the same second.

/*Random Number: InfoBrother:*/
 
#include <iostream>
#include <cstdlib> //required for rand() function:
#include <ctime> //required for time function: 
using namespace std;
 
main()
{
    srand((int)time(0));
    int i = 0;
    while(i++ < 10) 
    {
        int r = (rand() % 100) + 1;
        cout << r << " | ";
    }
 
    return 0;
}