# C++ Program to Implement the linear congruential generator for Pseudo Random Number Generation

C++Server Side ProgrammingProgramming

The linear congruential generator is a very simple example of a random number generator. It is one of the oldest and best-known pseudorandom number generator algorithms. The function which is used in this method −

Xn+1=(aXn + C) mod m

where X is the sequence of pseudorandom values, and

m,0<m— the “modulus"
a,0<a<m — the "multiplier"
c,0<c<m — the "increment"
X0, 0<x0<m — the "seed" or "start value"

are integer constants that specify the generator.

A benefit of this method is is that with appropriate choice of parameters, the period is known and long.

## Algorithm

Begin
Declare class mRND
Create a function Seed(number)
Assign a variable _seed=number
Create a constructor mRND
Declare _seed(0), a(0), c(0), m(2147483648)
Create a function rnd()
Return
_seed = (a * _seed + c) mod m
Declare a, c, m, _seed
Done
Declare an another subclass MS_RND inheriting from base class mRND
Create a constructor
Create a function rnd()
return mRND::rnd() right shift 16
Done
Declare an another subclass BSD_RND inheriting from base class mRND
Create a constructor
Create a function rnd()
return mRND::rnd()
Done
For x=0 to 6
Print MS_RAND
For x=0 to 6
Print BSD_RAND
Done
End

## Example Code

#include <iostream>
using namespace std;
class mRND {
public:
void seed(unsigned int s) {
_seed= s;
}
protected:
mRND() :
_seed(0), a(0), c(0), m(2147483648) { }
int rnd() {
return (_seed = (a * _seed + c) % m);
}
int a, c;
unsigned int m, _seed;
};
class MS_RND: public mRND {
public:
MS_RND() {
a = 214013;
c = 2531011;
}
int rnd() {
return mRND::rnd() >> 16;
}
};
class BSD_RND: public mRND {
public:
BSD_RND() {
a = 1016404597;
c = 12345;
}
int rnd() {
return mRND::rnd();
}
};
int main(int argc, char* argv[]) {
BSD_RND bsd_rnd;
MS_RND ms_rnd;
cout << "MS RAND:" << endl << "-----------" << endl;
for (int x = 0; x < 6; x++)
cout << ms_rnd.rnd() << endl;
cout << endl << "BSD RAND:" << endl << "-------------" << endl;
for (int x = 0; x < 6; x++)
cout << bsd_rnd.rnd() << endl;
return 0;
}

## Output

MS RAND:
-------
38
7719
21238
2437
8855
11797
BSD RAND:
--------
12345
1915290694
1005338679
629284700
741596485
1834373826