CODEWITHSUNDEEP
cnumbers
Shubh Roy
Shubh Roy

Reputation: 37

Why does my C program give different outputs in different compilers?

The result from my program is not what I expect and it is different on different compilers.

I have tried it on three compilers, two of which give the same result. But I want a combination of the two results.

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

int main()
{
    int iRandomNum = 0;
    int iUserInput = 0;
    const int VIP = 7;
    srand(time(NULL));
    iRandomNum = (rand() % 10) + 1;

    printf("\nGuess a number between 1 to 10.\n Make a wish and type in the number.\n");

    scanf("%d", &iUserInput);

    if(isdigit(iUserInput))
    {
         printf("\n\nYou did not enter a digit between 1 to 10.\n\n");
    }
    else
    {
        if(iUserInput==iRandomNum || iUserInput==VIP)
            printf("\n\nYou guessed it right!\n\n\n");
        else
            printf("\n\nSorry the right answer was %d.\n\n\n", iRandomNum);
    }
    return 0;
}

When I choose any number, the program should only alert me if I have not chosen the correct number in this number guessing game. But in the case of 7, we always have the right answer. This happens in the two online compilers. But in clang, when I do this & does not work. The isdigit function does not work then

Upvotes: 1

Views: 94

Answers (1)

Blaze
Blaze

Reputation: 16876

Using the %d format specifier, you're reading an int into iUserInput. That's correct, but then you use isdigit to try to see whether the number is between 1 and 10. However, this function is for finding out whether a char is between '0' and '9'. That's not the same - assuming ASCII those chars are equal to to 48 and 57 respectively. So You isdigit check most likely finds out whether the inputted number is between 48 and 57 (although there's no guarantee that ASCII is used, so a different encoding might lead to different results).

Instead, the check should be:

if((iUserInput >= 1) && (iUserInput <= 10)) {...}

Upvotes: 3

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