**Creating random integers within a specific range** in the C programming language is not as straightforward as it may seem. C itself does not have a dedicated function for this, but it does provide a variety of tools which can be combined to achieve this. The concept behind generating these numbers revolves around utilizing random numbers and a specific range.

Literally speaking, random numbers generated within specific ranges can be quite handy in a lot of applications in the programming world, like creating unique IDs, Computer Graphics, Games, Simulations, Testing and many more.

Contents

## The Libraries and Functions in Random Number Generation

To generate random numbers in C, we use the **stdlib.h** and **time.h** libraries. The **rand()** function is a part of the stdlib.h library, and because it does not take any arguments, it generates the same sequence of random numbers every time we run the program. To curb this, we use the **srand()** function which changes the seed of the pseudo-random generator.

#include

#include

#include

int main(){

srand(time(0));

for(int i = 0; i<5; i++){
printf(" %d ", rand());
}
return 0;
}
[/code]

## Solution: Generating Random Numbers within a Specific Range

The above code will generate any random number. To generate a random number within a specific range, you can use this formula: **(rand() % (upper – lower + 1)) + lower** where lower is the lower limit and upper is the upper limit of the range you want the random numbers within.

Here is a step-by-step breakdown of the entire process:

- Firstly, we use the
**time()**function to get the current time of the system. - Then, we use the
**srand()**function to seed the random generator. - After that, we use the
**rand()**function to generate the random number. - Finally, we bring the generated number within the desired range using the formula mentioned above.

Here’s an example code snippet:

#include

#include

#include

int main(){

int lower = 50, upper = 100;

srand(time(0));

for(int i = 0; i<5; i++){
printf(" %d ", (rand() % (upper - lower + 1)) + lower);
}
return 0;
}
[/code]
In the code snippet above, the random numbers generated will be within the range of 50 and 100.

## Demystifying the Code

Notice that we passed `time(0)` to the **srand()** function. This is to ensure that our random numbers are as random as possible. **time()** returns the current calendar time which changes every second, hence it’s a good idea to use it to seed our random number generator.

The formula `(rand() % (upper – lower + 1)) + lower` might look confusing at first glance, but it’s quite simple. **rand()** generates a random number. When we take the modulus of this number with `(upper – lower + 1)`, we are basically getting the remainder of the division of the number by `(upper – lower + 1)`. The result of the modulus operation is always less than the divisor. By adding the lower limit, we ensure that our random number is at least the lower limit.

Now you can generate random numbers within any given range in C! Happy Programming!