keil中用C语言16进制转二进制的代码

以下是用C语言实现16进制转换为二进制的代码：

#include <stdio.h>

int main() {
    char hex[17];
    long long binary = 0;
    int i = 0;

    // 读入16进制数
    printf("请输入16进制数：");
    scanf("%s", hex);

    // 转换为二进制
    while (hex[i]) {
        switch (hex[i]) {
            case '0':
                binary = binary * 16 + 0;
                break;
            case '1':
                binary = binary * 16 + 1;
                break;
            case '2':
                binary = binary * 16 + 10;
                break;
            case '3':
                binary = binary * 16 + 11;
                break;
            case '4':
                binary = binary * 16 + 100;
                break;
            case '5':
                binary = binary * 16 + 101;
                break;
            case '6':
                binary = binary * 16 + 110;
                break;
            case '7':
                binary = binary * 16 + 111;
                break;
            case '8':
                binary = binary * 16 + 1000;
                break;
            case '9':
                binary = binary * 16 + 1001;
                break;
            case 'A':
            case 'a':
                binary = binary * 16 + 1010;
                break;
            case 'B':
            case 'b':
                binary = binary * 16 + 1011;
                break;
            case 'C':
            case 'c':
                binary = binary * 16 + 1100;
                break;
            case 'D':
            case 'd':
                binary = binary * 16 + 1101;
                break;
            case 'E':
            case 'e':
                binary = binary * 16 + 1110;
                break;
            case 'F':
            case 'f':
                binary = binary * 16 + 1111;
                break;
            default:
                printf("输入的不是16进制数。\n");
                return 0;
        }
        i++;
    }

    printf("二进制数为：%lld", binary);

    return 0;
}

这个程序会要求用户输入一个16进制数，然后将其转换为二进制数，并输出结果。注意，这个程序只能处理一个16进制数，如果输入多个16进制数，只会处理第一个。