C中未声明的标识符

Question

我正在尝试在 Visual Studio 2012 Express 中用 C 语言编译一个小型银行程序。它向我显示了几乎所有变量的这个错误“未声明的标识符”，而这个也显示了“语法错误：缺少';'在'type'之前"。请告诉我正确的语法。谢谢。

#include<stdio.h>
#include<conio.h>
int main()
{
printf("Welcome to skybank\n");
int deposit,withdraw,kbalance;
char option;
printf("Press 1 to deposit cash\n");
printf("Press 2 to Withdraw Cash\n");
printf("Press 3 to Know Your Balance\n");
scanf_s("%c",option);
int decash,wicash;
switch(option)
{
int balance;
printf("Enter your current Balance\n");
scanf_s("%d",&balance);
case 1:
    printf("Enter the amount you want to deposit\n");
    scanf_s("%d",&decash);
    printf("Thank You\n");
    printf("%d have been deposited in your account\n",decash);
    break;
case 2:
    printf("Enter the amount you want to withdraw\n");
    scanf_s("%d",&wicash);
    int wibal;
    wibal=balance-wicash;
    printf("Thank You\n");
    printf("%d have been withdrawed from your account\n",wicash);
    printf("Your balance is %d\n",wibal);
    break;
case 3:
    printf("Your balance is Rs.%d\n",balance);
    break;
default:
    printf("Invalid Input\n");
    break;
}
getchar();
}

Answer 1

Microsoft C 编译器仅支持该语言的 25 年旧版本。限制之一是所有变量必须在任何其他语句之前声明。所以把你所有的变量声明移到函数的顶部。

我可以看到的下一个错误是将scanf_s 与%c 格式字符串一起使用。您必须传递一个指向变量的指针，并传递要读取的字符数。

scanf_s("%c", &option, 1);

同样你需要传递一个地址来读取balance。

您还需要更改 switch 语句，使其仅包含案例。将裸指令移到外面。

您对option 的阅读将不起作用。因为当您检查1 时，您正在检查具有ASCII 代码1 的字符。将option 更改为int 并使用%d 读取。

也许你正在寻找这样的东西：

#include<stdio.h>
#include<conio.h>

int main(void)
{
    int deposit,withdraw,kbalance;
    int option;
    int decash,wicash;
    int balance;
    int wibal;

    printf("Welcome to skybank\n");
    printf("Press 1 to deposit cash\n");
    printf("Press 2 to Withdraw Cash\n");
    printf("Press 3 to Know Your Balance\n");
    scanf_s("%d", &option);
    printf("Enter your current Balance\n");
    scanf_s("%d", &balance);
    switch(option)
    {
        case 1:
            printf("Enter the amount you want to deposit\n");
            scanf_s("%d", &decash);
            printf("Thank You\n");
            printf("%d have been deposited in your account\n", decash);
            break;
        case 2:
            printf("Enter the amount you want to withdraw\n");
            scanf_s("%d", &wicash);
            wibal=balance-wicash;
            printf("Thank You\n");
            printf("%d have been withdrawed from your account\n", wicash);
            printf("Your balance is %d\n", wibal);
            break;
        case 3:
            printf("Your balance is Rs.%d\n", balance);
            break;
        default:
            printf("Invalid Input\n");
            break;
    }
    getchar();
}

Answer 2

对于未识别的变量，尝试将所有变量声明放在主块的顶部，例如：

int main()
{
    int deposit, withdraw, kbalance, decash, wicash, wibal;
    char option;
    printf("Welcome to skybank\n");

C 的旧变体不喜欢​​将变量声明与代码混合。据我所知，微软 C 实现的 C 标准是 C99 之前的标准，所以这可能是问题所在。

您应该研究的其他一些问题：

scanf_s("%c",option); - option 应该是 &option，因为您正在获取指向该变量的指针。

也在这里：case 1:

你想要'1'（如case '1'）而不是普通的1，因为它是char，而不是你想要的int。

其他 case 检查也是如此。

关于scanf_s的问题，尝试编译时有警告，应该已经被编译器指出了。

最后，您可能希望在代码中删除不使用的变量，例如 kbalance、withdraw 和 deposit。

Answer 3

在Visual c的变量声明中块的开头做。

例如

int main()
{
    int deposit,withdraw,kbalance;
    char option;
    int decash,wicash
    int balance;
    int wibal;
...

Answer 4

试试这个代码：

#include<stdio.h>
#include<stdlib.h>
int main()
{
    printf("Welcome to skybank\n");
    int deposit,withdraw,kbalance;
    char option;
    printf("Press 1 to deposit cash\n");
    printf("Press 2 to Withdraw Cash\n");
    printf("Press 3 to Know Your Balance\n");
    scanf("%c",&option);
    int decash,wicash;
    switch(option)
    {
    int balance;
    printf("Enter your current Balance\n");
    scanf("%d",&balance);
    case 1:
        printf("Enter the amount you want to deposit\n");
        scanf("%d",&decash);
        printf("Thank You\n");
        printf("%d have been deposited in your account\n",decash);
        break;
    case 2:
        printf("Enter the amount you want to withdraw\n");
        scanf("%d",&wicash);
        int wibal;
        wibal=balance-wicash;
        printf("Thank You\n");
        printf("%d have been withdrawed from your account\n",wicash);
        printf("Your balance is %d\n",wibal);
        break;
    case 3:
        printf("Your balance is Rs.%d\n",balance);
        break;
    default:
        printf("Invalid Input\n");
        break;
    }
    getchar();
}

Answer 5

移动这个：

int balance;
printf("Enter your current Balance\n");
scanf_s("%d",&balance);

在switch 语句之前。