帮我写一个计算器加减乘除的C语言代码

在C语言中编写一个简单的命令行计算器，可以处理基本的加减乘除操作，可以参考下面这个示例代码：

#include <stdio.h>

// 定义计算函数
int add(int a, int b) {
    return a + b;
}

int subtract(int a, int b) {
    return a - b;
}

int multiply(int a, int b) {
    return a * b;
}

int divide(int a, int b) {
    // 防止除数为0的情况
    if (b == 0) {
        printf("Error: Division by zero is not allowed.\n");
        return 0;
    }
    return a / b;
}

int main() {
    int num1, num2, choice;
    
    printf("Enter operation (+, -, *, /): ");
    scanf("%d", &choice);

    printf("Enter two numbers: ");
    scanf("%d %d", &num1, &num2);
    
    switch(choice) {
        case '+':
            printf("Result: %d\n", add(num1, num2));
            break;
        case '-':
            printf("Result: %d\n", subtract(num1, num2));
            break;
        case '*':
            printf("Result: %d\n", multiply(num1, num2));
            break;
        case '/':
            printf("Result: %d\n", divide(num1, num2));
            break;
        default:
            printf("Invalid operation! Please enter +, -, *, or /\n");
    }

    return 0;
}