打印字符串给出字节C

参见英文答案 > How do I print a non-null-terminated string using printf?????????????????????????????????????2个
当我编写简单的代码来将简单的字母序列编码为字节并再次解码时,我遇到了解码问题.一切都在完成我想要有4个字符的序列,但它也包括最后的字节.这是我的代码：

char* B2T(int num) {
    unsigned char temp;
    char res[4];
    int sw[] = { 6,4,2,0 };
    char tab[4] = { 'A','C','G','T' };
    int i = 0;
    for (int i = 0; i < 4; i++) {
        res[i] = tab[(num >> sw[i]) & 3];
    }
    printf_s("%sn",res); //!!!!!!problem here!!!!!!!!
    return res;
}

int main() {
    FILE *I,*O;
    char tab[5],opt;
    int res,i,temp;
    bool work = true;
    while (work) {
        printf_s("nChoose option: decode or encode (d/e): ");
        scanf_s("%c",&opt);
        switch (opt) {
        case 'e':
            fopen_s(&I,"DNA.txt","r");
            fscanf_s(I,"%s",&tab,5);
            fopen_s(&O,"result.bin","a");
            while (feof(I) == 0) {
                res = T2B(tab);
                printf_s("%X ",res);
                fprintf_s(O,"%X ",res);
                fscanf_s(I,5);
            };
            fclose(I);
            fclose(O);
            break;
        case 'd':
            fopen_s(&I,"%X",&temp);
            while (feof(I)==0) {
                char* ress = B2T(temp);
                fscanf_s(I,&temp);
            }
            fclose(I);
            break;
        }
    }
    return 0;
}

char res[5];
res[4] = '';

while (feof(I) == 0)