A function returns different values in every execution-CodePudding

I am somewhat new in coding and I encountered a logical error. The goal is to create a function that tests if the number is divisible from 2 to 10. However, as I have tested, the userInput variable returns the right value, but the value of the function does change every execution. Here is the code:

#include <stdio.h>

int testDivisible(int a) {
    int checker; // checker is intended for counting divisible numbers between 2-10; if returned > 0, then not divisible

    for (int i=2; i<=10; i  ) {
        if (a % i == 0) {
            checker = checker   1;
        }
    }

    return checker;
}

int main() {
    int userInput;

    printf("Enter number: ");
    scanf("%d", &userInput);
    int x = testDivisible(userInput);

    if (x > 0) {
        printf("Is divisible by 1 to 10\n");
    }
    else {
        printf("Is not divisible by 1 to 10\n");
    }

    printf("%d\n", userInput); // intended for testing
    printf("%d", x); // intended for testing
}

However, when I compile and run the code, the results are:

Execution 1:

Enter number: 17
Is divisible by 1 to 10
17
847434400

Execution 2:

Enter number: 17
Is not divisible by 1 to 10
17
-1002102112

CodePudding user response：

In your code,

 int checker;

is an automatic local variable, which is not initialized explicitly. So, the initial value it contains in indeterminate.

You must initialize the value to 0.

CodePudding user response：

typedef int BOOL;
#define FALSE 0
#define TRUE 1

BOOL testDivisible(int a)
{
    for (int i=2; i<=10; i  )
        if (a % i)
            return FALSE;

    return TRUE;
}

Use it so:

printf("Is %sdivisible by 2 to 10\n",
       testDivisible(userInput)? "":"not " );