"Guess the number Game" in C

Just started learning C. I hope my code adheres to best practices and idioms

#include 
#include 
#include 
#include 
int main(void)
{
int iRandomNum;
int iGuess;
srand(time(NULL));

iRandomNum = (rand() % 10);
printf("Guess a number between 1 and 10:");
scanf("%d", &iGuess);

// isdigit function expects a character so the guess value has to be ascii value of the digit character 
iGuess += 48;
if (isdigit(iGuess)){
    iGuess -=48; // change back to the original value for comparison with random number
    if (iGuess == iRandomNum){   
        printf("You Guessed Correctly\n");
     }    
    else{
        printf("The correct answer was %d\n",iRandomNum);
        printf("You guessed %d\n",iGuess);
     }   
 }   
 else{
      printf("This is not a digit!\n");
 }
 }

I have observed a few things that may help you improve your code.

Use consistent formatting

The code as posted has inconsistent indentation which makes it hard to read and understand. Pick a style and apply it consistently.

Check return values for errors

The call to scanf can fail. You can check the return values to make sure they haven't or your program may crash (or worse) when given malformed input or due to low system resources. Rigorous error handling is the difference between mostly working versus bug-free software. You should strive for the latter.

Don't use Hungarian notation

Prefixing every variable with an abbreviation of its type is usually called "Hungarian notation" and it was once popular. Even then it was a bad idea. Don't clutter up your source code with that; instead, concentrate on defining meaningful names for each variable and choose types appropriately. I'd suggest secretNumber and userGuess in this case.

Use a better random number generator

You are currently using

iRandomNum = (rand() % 10);

There are a number of problems with this approach. The most significant problem is that the range this returns (0 through 9 inclusive) does not match what the user is asked to guess ("a number between 1 and 10") Second, this will generate lower numbers more often than higher ones -- it's not a uniform distribution. Another problem is that the low order bits of the random number generator are not particularly random, so neither is the result. On my machine, there's a slight but measurable bias toward 0 with that. See this answer for details, but I'd recommend changing that to

secretNumber = rand() / (RAND_MAX / 10) + 1;

Think of the user

When someone asks me to "Guess a number between 1 and 10", I usually say \$e\$. (Yes, I'm afraid I'm that kind of person.) It seems clear from the context of your program that what you really mean is to guess an integer, and it seems likely that, technically speaking, you don't want numbers solely between 1 and 10 but that you mean to include 1 and 10 among the possible choices. To more clearly convey that, I'd suggest asking the user to "guess a whole number from 1 to 10 inclusive" but I'm probably too used to being around engineers and scientists.

Check your logic

If I input "e" as my guess, the scanf call will fail and the variable may be uninitialized.

StackExchange Code Review Q#156219, answer score: 13