int getchar() {
    register char c asm ("al");
    asm volatile (
            "movb $0x00, %%ah\n\t"
            "int $0x16"
            : "=r" (c)
            :: "ah", "cc"
            );
    return c;
}

int putchar(int c) {
    asm volatile (
            "push %%bp          \n\t"
            "mov %0, %%ax      \n\t"
            "movb $0x0e, %%ah   \n\t"
            "movb $0, %%bh      \n\t"
            "int $0x10          \n\t"
            "pop %%bp           \n\t"
            :: "r" (c)
            : "ax", "bh", "cc"
            );
    return 0;
}

int puts(const char* s) {
    while (*s) {
        putchar(*s++);
    }
    return 0;
}