用c语言编程实现一个简单的计算器，具备加法，减法，乘法，除法，阶乘等运算

好的，以下是 C 语言的实现示例：

#include <stdio.h>

int add(int x, int y) {
    return x + y;
}

int subtract(int x, int y) {
    return x - y;
}

int multiply(int x, int y) {
    return x * y;
}

float divide(int x, int y) {
    if (y == 0) {
        printf("Error: Division by zero is not allowed\n");
        return 0;
    } else {
        return (float)x / y;
    }
}

int factorial(int x) {
    if (x < 0) {
        printf("Error: Factorial of a negative number is not defined\n");
        return 0;
    } else if (x == 0) {
        return 1;
    } else {
        return x * factorial(x-1);
    }
}

int main() {
    int choice, num1, num2;
    printf("Select operation.\n");
    printf("1.Add\n");
    printf("2.Subtract\n");
    printf("3.Multiply\n");
    printf("4.Divide\n");
    printf("5.Factorial\n");

    scanf("%d", &choice);

    switch (choice) {
        case 1:
            printf("Enter first number: ");
            scanf("%d", &num1);
            printf("Enter second number: ");
            scanf("%d", &num2);
            printf("%d + %d = %d\n", num1, num2, add(num1, num2));
            break;
        case 2:
            printf("Enter first number: ");
            scanf("%d", &num1);
            printf("Enter second number: ");
            scanf("%d", &num2);
            printf("%d - %d = %d\n", num1, num2, subtract(num1, num2));
            break;
        case 3:
            printf("Enter first number: ");
            scanf("%d", &num1);
            printf("Enter second number: ");
            scanf("%d", &num2);
            printf("%d * %d = %d\n", num1, num2, multiply(num1, num2));
            break;
        case 4:
            printf("Enter first number: ");
            scanf("%d", &num1);
            printf("Enter second number: ");
            scanf("%d", &num2);
            printf("%d / %d = %.2f\n", num1, num2, divide(num1, num2));
            break;
        case 5:
            printf("Enter a non-negative integer: ");
            scanf("%d", &num1);
            printf("%d! = %d\n", num1, factorial(num1));
            break;
        default:
            printf("Invalid Input\n");
    }

    return 0;
}

这个程序会根据用户的选择进行不同的计算操作，使用了函数来实现每种运算，同时还有对除零和负数阶乘的错误处理。注意输出浮点数除法结果时使用了 `%.2f` 格式化字符串控制输出精度。