Issue forcing a return -1 from function in C

Question

Creating a banker's program in beginner's C class. All of my code works successfully (after testing all cases), except for forcing a return of negative one in part of the loop. When the value is returned by copy to the main program it alters the balance.

Function return

  else { //If the amount to be withdrawn from the account is greater than the existing amount
        printf("Error. Withdrawal must be less than account balance.\n"); //Output error message
        return -1; //Return a negative one to the main program
  }

Return by copy in main

case 3: //Cash Withdrawal

        printf("You are about to withdraw cash from an account.\n \n");
        withdrawnAmount = withdrawal(balance); //Calling function to withdraw money from existing account
        balance -= withdrawnAmount;
        printf("Your new account balance is $%d\n\n", balance);
        break;

Answer 1

I think in that case you should either return 0; so that the amount will not be deducted, like this:

 else { //If the amount to be withdrawn from the account is greater than the existing amount
        printf("Error. Withdrawal must be less than account balance.\n"); //Output error message
        return 0; //Return zero to the main program
  }

Or, if you want to keep using the negative one, you would need to check the value returned before deducting from the account balance, as follows:

case 3: //Cash Withdrawal
    printf("You are about to withdraw cash from an account.\n \n");
    withdrawnAmount = withdrawal(balance); //Calling function to withdraw money from existing account
    if(withdrawnAmount > 0)
       balance -= withdrawnAmount;
    else
       printf("-1");
    printf("Your new account balance is $%d\n\n", balance);
    break;

Hope it helps.