beit.c

static const char *layout[3][3] = {
	{"1","2","3"}, 
	{"4","5","6"},
	{"7","8","9"}
};

static char layout2[3][3] = {
	{1,2,3}, 
	{4,5,6},
	{7,8,9}
};

static char *itoa(int value, char *str, int base)
{
	char *rc, *ptr, *low;

	/* Early exit for unsupported bases */
	if (base < 2 || base > 36 ) {
		*str = '\0';
		return str;
	}

	rc = ptr = str;

	if (value < 0 && base == 10)
	{
		*ptr++ = '-';
		value = -value;
	}

	low = ptr;

	do {
		*ptr++ = "0123456789abcdefghijklmnopqrstuvwxyz"[value % base];
		value /= base;
	} while (value);

	*ptr-- = '\0';

	while (low < ptr)
	{
		char tmp = *low;
		*low++ = *ptr;
		*ptr-- = tmp;
	}

	return rc;
}

void print(const char *s, int offset, char color)
{
	char *d = (char *)0xb8000;

	offset *= 2;

	while (*s)
	{
		d[offset+0] = *s++;
		d[offset+1] = color;

		d += 2;
	}
}

static void grid(void)
{
	int count = 0;
	char str[128];

	for (int i = 0; i < 3; i++ ){
		for (int j = 0; j < 3; j++ ){
				layout2[i][j] = *itoa(count, str, 10);
				count++;
		}
	}

	print(layout[0][0], 80*5, 0x17);
	print(&layout2[0][1], 80*6, 0x17);
}

static void clear_screen(void)
{
	char *d = (char *)0xb8000;
	unsigned int i=0;

	for(i = 0; i < 80*25*2; i += 2)
	{
		d[i+0] = ' ';
		d[i+1] = 0x11; /* Macro me to COLOR_BLANK or something */
	}
}

int k_main()
{
	clear_screen();
	print("Kernel", 80*2, 0x17);
	grid();
	while(1)
		;
}