任意輸入四位十六進位制整數，以反序方式輸出

#include <stdio.h>

void fun1(unsigned short a) {
    unsigned short b;

    printf("========\t");
    printf("%#X\t", (unsigned short) (a << 12) >> 12 << 12);
    printf("%#X\t", (unsigned short) (a << 8) >> 12 << 8);
    printf("%#X\t
 
", (unsigned short) (a << 4) >> 12 << 4);
    printf("%#X\t", (unsigned short) (a << 0) >> 12 << 0);
    printf("========\t");

    b = (unsigned short) (a << 12) >> 12 << 12; // D000
    b += (unsigned short) (a << 8) >> 12 << 8; // D000 + C00
 

    b += (unsigned short) (a << 4) >> 12 << 4; // DC00 + B0
    b += (unsigned short) (a << 0) >> 12 << 0; // DCB0 + A

    printf("%#X\t", b);
    printf("========\n");
}

void fun2(unsigned short a) {
    unsigned short b;

    printf("========\t");
    printf("%X\t", (a & 0x000F
 
) << 12);
    printf("%X\t", (a & 0x00F0) << 4);
    printf("%X\t", (a & 0x0F00) >> 4);
    printf("%X\t", (a & 0xF000) >> 12);
    printf("========\t");

    b = (a & 0x000F) << 12;
    b += (a & 0x00F0) << 4;
    b += (a & 0x0F00) >> 4;
    b += (a & 0xF000) >> 12;

    printf("%X\t", b);
    printf("========\n");
}

/**
* 四位十六進位制反序：ABCD => DCBA
*/
int main() {
    // char 0000 0000
    // short 0000 0000 0000 0000
    unsigned short a = 0XABCD;

    // scanf("%4X", &a);

    printf("%X\n", a);

    fun1(a);
    fun2(a);
}