While 循环和 getchar 函数辅助

Question

我是 C 编程的新手，我在做这个问题时遇到了一些问题，需要我使用 while 循环和嵌套的 switch 函数。 如果用户在循环开始时输入为 -1，则切换终止。

我应该使用 getchar() 函数来确定 while 循环是否继续。

我试图用 -1 替换 EOF，但后来发现 getchar() 只能读取一个字符。 '-1' 是两个字符。 它还读取一个字符，如果它是一个整数，将始终作为无符号整数返回。

内容没问题，我只是在 while 循环和 getchar 函数中遇到问题：

 while (paycode = getchar()) != EOF)

将导致 while 循环结束的输入应该是-1 。 我也面临一个问题，由于某种原因， prinf("Enter pacode")重复两次。 我知道代码看起来有点凌乱和未优化，请原谅！

任何建议、优化、建议和反馈将不胜感激。 附件是我的代码示例。

int main(void)

{
    int paycode, managersalary, grossweeklysales, overtime;
    float hourlysalary,comissionsalary ,piecepay, piecenumber, piecewage;

    unsigned int totalhours, managercount = 0, hourlycount = 0, comissioncount = 0 , piececount = 0;

    printf("Enter paycode (-1 to end): ");

    while ( (paycode = getchar()) != EOF) { //How to replace by EOF with -1? Do I use default: then?
        //what If I use switch loop only or with a for loop?


        switch (paycode) {

        case '1':
            printf("Manager selected.\n");
            printf("Enter weekly salary: ");
            scanf("%d", &managersalary);
            printf("Manager's pay is $%d", managersalary);

            managercount++;
                break;

        case '2':
            printf("Hourly worker selected.\n");
            printf("Enter hourly salary: ");
            scanf("%f", &hourlysalary);
            printf("Enter total hours worked: ");
            scanf("%d", &totalhours);
                    
            if (totalhours > 40) {
                overtime = totalhours - 40;
                printf("Worker worked %d overtime hours\n", overtime);
            }
                
                printf("Worker's pay is $%.2f.", (hourlysalary*40)+(1.5*hourlysalary)*overtime);
                    break;  

        case'3':
            printf("Comission worker selected.\n");
            printf("Enter gross weekly sales: ");
            scanf("%d", &grossweeklysales);
            comissionsalary = 250 + grossweeklysales*(5.7 / 100);
            printf("Comission worker's pay is $%.2f", comissionsalary);

            comissioncount++;
                break;

        case '4':
            puts("Pieceworker selected.");
            printf("Enter number of pieces: ");
            scanf("%f", &piecenumber);
            printf("Enter number of pieces: ");
            scanf("%f", &piecewage);
            piecepay = piecenumber * piecewage;

            printf("Pieceworker's pay is $%.2f", piecepay);

            piececount++;
            break;
            
        }
        printf("Enter paycode (-1 to end): ");