c++ - 这段 C++ 代码有什么问题？ (未声明的标识符)

Question

出现此错误:(68): error C2065: 'programend' : undeclared identifier

(题外话:我知道使用 using namespace std 是不好的做法，但我不想在所有内容前面键入 std::。但是，如果这是导致错误的原因，我会的。)

代码如下:

#include <iostream>

using namespace std;

int main(void) {
    do{
    system("title Mini-Calc");
    cout << "Hello World!  Welcome to Dustin's C++ Calculator!" << endl;
    cout << "To get started, enter a number:" << endl;

    int operation;
    double num1, num2, answer;

    cin >> num1;
    cout << "Now enter another number:" << endl;
    cin >> num2;

    cout << "Please type the corrresponding number for the operation desired, and press enter." << endl;
    cout << "1 = +, 2 = -, 3 = x, 4 = /" << endl;

    cin >> operation;

    switch(operation) {
        case 1:
            answer=num1+num2;
        break;

        case 2:
            answer=num1-num2;
        break;

        case 3:
            answer=num1*num2;
        break;

        case 4:
            answer=num1/num2;
        break;

    }

    cout << "The answer is: " << endl;
    cout << answer << endl;

    bool programend;

    cout << "Would you like to end the program? (y for yes, n for no)" << endl;

    cin >> programend;

    switch(programend) {
        case 'y':
            programend=true;
        break;

        case 'n':
            programend=false;
        break;

        case 'Y':
            programend=true;
        break;

        case 'N':
            programend=false;
        break;
        }
    } while (programend==false);
    return 0;
}

Answer 1

如果你取出 do...while 内容，你会看到 programend 没有在正确的范围内声明:

int main(void) {
    do{
        ...
    } while (programend==false);
    return 0;
}

它应该在 main 和 do 之间声明为可用。