把复数计算器中的扫描运算符放在扫描数字之前会出现错误，但放在数字之后则不会出错。

在编写复数计算器的代码时，应该先扫描数字，然后扫描运算符。下面是一个示例代码：

#include<stdio.h>

int main()
{
    float real1, real2, imag1, imag2;
    char operator;

    printf("Enter first complex number (in the form a+bi): ");
    scanf("%f+%fi", &real1, &imag1); // 先扫描数字

    printf("Enter operator (+,-,*,/): ");
    scanf(" %c", &operator); // 再扫描运算符

    printf("Enter second complex number (in the form a+bi): ");
    scanf("%f+%fi", &real2, &imag2); // 再扫描数字

    switch(operator)
    {
        case '+':
            printf("Sum = %.2f + %.2fi\n", real1+real2, imag1+imag2);
            break;
        case '-':
            printf("Difference = %.2f + %.2fi\n", real1-real2, imag1-imag2);
            break;
        case '*':
            printf("Product = %.2f + %.2fi\n", real1*real2-imag1*imag2, real1*imag2+real2*imag1);
            break;
        case '/':
            printf("Quotient = (%.2f + %.2fi) / (%.2f + %.2fi)\n", real1*real2+imag1*imag2, imag1*real2-real1*imag2, real2*real2+imag2*imag2);
            break;
        default:
            printf("Invalid operator.\n");
    }

    return 0;
}