c 十进制转换成十六进制

//输入一个整数，转化成十六进制N，nL nH 分别为无符号型双字节整数 N 的低位和高位字节
#include<stdio.h>
int main() 
{
    int a, b, i;
    char s[10];
 char arr[10];
 
    scanf("%d",&a);
 
    if(a == 0)
    {
        printf("error input\n");
        return 0;
    }
 
    i = 0;
    while(a > 0)
    {
        b = a%16;
        if(b < 16)
            s[i] =  b;
        i++;
        a = a / 16;
    }
 printf("i = %d\n",i);
 
 if(i==4)
 {
 arr[8] |= s[3]<<4;
 arr[8] |= s[2];
 arr[9] |= s[1]<<4; 
 arr[9] |= s[0];
 }else if(i==3){
 arr[8] |= s[2];
 arr[9] |= s[1]<<4; 
 arr[9] |= s[0];
 }else if(i==2){
 arr[8] = 0;
 arr[9] |= s[1]<<4; 
 arr[9] |= s[0];
 }else{
 arr[8] = 0;
 arr[9] = s[0];
 }
 
    for(i--; i >= 0; i--)
 {
 printf("%d\n", s[i]);


 }


 printf("arr[8] = %x \n",arr[8]);
 printf("**********\n");
 printf("arr[9] = %x \n",arr[9]);


    return 0;
}