Generate Random Numbers Between 10 and 20 in C

This code demonstrates how to create a C function called 'random_number' to generate random integers between 10 and 20. It utilizes the rand() function for random number generation and srand() for seeding the random number generator.

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

int random_number() {
    int random = rand() % 11 + 10;  // generate a random number between 10 and 20
    return random;
}

int main() {
    srand(time(NULL));  // seed the random number generator with the current time

    int result = random_number();
    printf('%d
', result);

    return 0;
}

Explanation:

1. random_number() Function:

   • rand() % 11 + 10: This expression is crucial for generating numbers within the desired range.
     • rand(): The rand() function produces a pseudo-random integer. This integer is typically within a large range (e.g., 0 to RAND_MAX, which is a system-defined constant).
     • % 11: The modulo operator (%) divides the random number by 11 and returns the remainder. This ensures the result is between 0 and 10.
     • + 10: Adding 10 shifts the range to 10 to 20.

2. srand(time(NULL)):

   • time(NULL): This function obtains the current time in seconds since the Unix epoch. This value is used to seed the random number generator.
   • srand(): The srand() function initializes the random number generator. By seeding it with the current time, the generator will produce a different sequence of random numbers each time the program runs.

Important Considerations:

• Seeding: It's essential to call srand(time(NULL)) only once at the beginning of your program. Multiple calls within a short time can lead to the same random number sequence.
• Randomness: Keep in mind that these are pseudo-random numbers. They are generated using an algorithm, so they are not truly random.

This code provides a foundation for working with random numbers in C. You can adapt this function to generate random numbers within any desired range using the same principle of modulo and shifting.