rand() function in C++

In this guide, you will learn what is rand() function is in C++ programming and how to use it with an example.

1. rand() Function Overview

The rand() function is used to generate random numbers in a range from 0 to RAND_MAX. Typically, this function is used in conjunction with the srand() function to seed the random number generator for varying sequences of numbers. It is a part of the C standard library <cstdlib> in C++.

Signature:

int rand(void);

Parameters:

None.

2. Source Code Example

#include <iostream>
#include <cstdlib>
#include <ctime>

int main() {
    // Seed the random number generator with current time
    srand(time(0));

    // Print 5 random numbers
    for(int i = 0; i < 5; i++) {
        std::cout << "Random number " << (i+1) << ": " << rand() << std::endl;
    }

    return 0;
}

Output:

(Randomized output every execution. An example might look like:)
Random number 1: 2083453501
Random number 2: 176128037
Random number 3: 621356489
Random number 4: 123456789
Random number 5: 987654321

3. Explanation

1. Before generating random numbers, it's essential to seed the random number generator using srand(). Seeding it with the current time by passing time(0) ensures a different sequence of random numbers every time the program is executed.

2. We then use the rand() function in a loop to generate and print 5 random numbers.

3. Each time rand() is called, it returns a pseudo-random number between 0 and RAND_MAX.