## Dev C++ Random Number

07.06.2020by

C program to generate random numbers randomize – this function is used to generate random numbers each time, when you run program. Rand – this function is used to return random number from 0 to RANDMAX-1. Well attempted at making a unique random number generator using arrays and functions. Well attempted at making a unique random number generator using arrays and functions, but it still will not work and I cannot. Software Development Forum Discussion / Question. C Random number generator. Compatibility In C, the generation algorithm used by rand is guaranteed to only be advanced by calls to this function. In C, this constraint is relaxed, and a library implementation is allowed to advance the generator on other circumstances (such as calls to elements of random). Rand produces a random number not a random order, moreover the chances are that in that short loop it is producing a unique number each time but the%9 operation is restricting the value to a small range. (12% 9) has the same value as (21% 9) for example, each is equally likley on each iteration. With rng-tools, hardware random number generators like Entropy Key, etc. Can write to /dev/random. The diehard tests programs dieharder, diehard and ent can test these random number generators. In January 2014, Daniel J. Bernstein published a critique of how Linux mixes different sources of entropy. He outlines an attack in which one source of. Through out this page, we're limited to pseudo-random numbers. We can generate a pseudo-random number in the range from 0.0 to 32,767 using rand function from library. The maximum value is library-dependent, but is guaranteed to be at least 32767 on any standard library implementation.

rand ()

rand() function is used in C to generate random numbers. If we generate a sequence of random number with rand() function, it will create the same sequence again and again every time program runs. Say if we are generating 5 random numbers in C with the help of rand() in a loop, then every time we compile and run the program our output must be the same sequence of numbers.
Syntax:

### Dev C++ Random Numbers

 `#include ``int``main(``void``) ``// This program will create same sequence of ``printf``(``' %d '``, ``rand``()); ``} `

NOTE: This program will create same sequence of random numbers on every program run.
Output 1:

Output 2:

Output n:

srand()

The srand() function sets the starting point for producing a series of pseudo-random integers. If srand() is not called, the rand() seed is set as if srand(1) were called at program start. Any other value for seed sets the generator to a different starting point.
Syntax:

Note: The pseudo-random number generator should only be seeded once, before any calls to rand(), and the start of the program. It should not be repeatedly seeded, or reseeded every time you wish to generate a new batch of pseudo-random numbers.
Standard practice is to use the result of a call to srand(time(0)) as the seed. However, time() returns a time_t value which vary everytime and hence the pseudo-random number vary for every program call.

 `#include ``#include ``// Driver program ``{ ``// This program will create different sequence of ``// Use current time as seed for random generator ``printf``(``' %d '``, ``rand``()); ``return``0; `

NOTE: This program will create different sequence of random numbers on every program run.
Output 1:

Output 2:

Output n:

How srand() and rand() are related to each other?

srand() sets the seed which is used by rand to generate “random” numbers. If you don’t call srand before your first call to rand, it’s as if you had called srand(1) to set the seed to one.
In short, srand() — Set Seed for rand() Function.

C program to generate pseudo-random numbers using rand and random function (Turbo C compiler only). As the random numbers are generated by an algorithm used in a function they are pseudo-random, this is the reason that word pseudo is used. Function rand() returns a pseudo-random number between 0 and RAND_MAX. RAND_MAX is a constant which is platform dependent and equals the maximum value returned by rand function.

## C programming code using rand

We use modulus operator in our program. If you evaluate a % b where a and b are integers then result will always be less than b for any set of values of a and b. For example
For a = 1243 and b = 100
a % b = 1243 % 100 = 43
For a = 99 and b = 100
a % b = 99 % 100 = 99
For a = 1000 and b = 100
a % b = 1000 % 100 = 0

In our program we print pseudo random numbers in range [0, 100]. So we calculate rand() % 100 which will return a number in [0, 99] so we add 1 to get the desired range.

#include <stdio.h>
#include <stdlib.h>

int main(){
int c, n; printf('Ten random numbers in [1,100]n');

for(c =1; c <=10; c++){
n =rand()%100+1;
printf('%dn', n);
}

return0;
}

If you rerun this program, you will get the same set of numbers. To get different numbers every time you can use: srand(unsigned int seed) function; here seed is an unsigned integer. So you will need a different value of seed every time you run the program for that you can use current time which will always be different so you will get a different set of numbers. By default, seed = 1 if you do not use srand function.

## C programming code using random function (Turbo C compiler only)

Function randomize is used to initialize random number generator. If you don't use it, then you will get same random numbers each time you run the program.

#include <stdio.h>
#include <conio.h>
#include <stdlib.h>

### Dev C Random Number Er Between 1 And

int main()
{
int n, max, num, c;

### C++ Random Number Generator

printf('Enter the number of random numbers you wantn');
scanf('%d',&n);

### C++ Random Number Range ### C++ Random Number Function

printf('Enter the maximum value of random numbern');
scanf('%d',&max);

printf('%d random numbers from 0 to %d are:n', n, max);
randomize();

### Dev C Random Number Er Generator

for(c =1; c <= n; c++)
{
num = random(max);
printf('%dn',num);
}

getch();
return0;
}