Debug Assertion Failed? : <p>I'm fairly new to coding (currently learning C) and I'm confused as to why this error occurs when I'm running the console.</p>

<p><a href="https://i.stack.imgur.com/JQ5XA.png" rel="nofollow noreferrer">The Error that I get.</a></p>

<p>Here's the code that I wrote (it's a function that I call in the main to run a simple calculator program), I'm still not completely done my switch, but I'm pretty sure it should work with just that! (I think).</p>

<pre><code>void part2() {

    printf("Welcome to Part 2!\n\n\nThis is a basic calculator!\nPlease select one of the following options:\n\n");
    printf("1) - Addition\n");
    printf("2) - Subtraction\n");
    printf("3) - Multiplication\n");
    printf("4) - Division\n");
    printf("0) - Exit Program\n\n");


    int selectionNum = 0;

    float operand1 = 0;
    float operand2 = 0;
    float result = 0;

    scanf_s("%d",selectionNum);

    switch (selectionNum) {

        case '1' :

            printf("_ + _ = _\n");
            printf("Please enter the first addend: ");
            scanf_s("%f", operand1);
            printf("\n\n");

            printf("%f", operand1);
            printf(" + _ = _\n");
            printf("Please enter the second addend: ");
            scanf_s("%f", operand2);
            printf("\n\n");

            result = operand1 + operand2;

            printf("%f", operand1);
            printf(" + ");
            printf("%f", operand2);
            printf(" = ");
            printf("%f", result);

            break;

        default :

            printf("\n\nYou entered an invalid option! :(\n Try again!");

    }

    printf("done.");

}
</code></pre>

<p>Does anyone know what might be the issue? :(</p>
