Note: Bit just has two options(0 or 1) so in the drawing function 1 means to draw a pixel(in any color we like) and 0 means to skip.

Take a look how the letter 'H' looks(In mode 13h) in the memory, the red lines seperate the BYTES.

And this is how it looks on the Screen as a BITMAP:

Character Drawing Function

#define CHARW 8 #define CHARH 8 unsigned char color = 15; void drawchar(int x, int y, char c) { char *work_byte; unsigned char work_bit = 128; work_byte = rom_font +(c << 3);//Character poistion in memory for (int iy = 0; iy < CHARH; iy++) { work_bit = 0x80;//Init the working bit, 'cause if we we are here, it means we start a new byte. for (int ix = 0; ix < CHARW; ix++) { if (*work_byte & work_bit) put_pixel(x +ix, y +iy, color); work_bit >>= 1;//Going to the next bit(/pixel) } work_byte++;//Going to the next Byte(/line) } }

Ok well you are confused from the bits, huh??
Well it's easy, but before I start, remember one important thing for the drawing function:BINARY SYSTEM is the basis for BITS!!!!(duh)

work_bit is 128, which is the last bit which is the first pixel. :)
work_byte is the starting position of the font plus character's value multipled by 8(As i said above).
if (*work_byte & work_bit) - here, we check whether the bit is 1 or 0(If the result is 1, we draw the pixel)
We read the pointer of work_byte 'cause we want the byte it points on, not the number of the byte it points.
And then we ADD(LOGIC) the work_bit to the work_byte, so we actually check whether the bit(work_bit) is 1 in the byte.
work_bit >>= 1 is the same as work_bit /= 2 - We do this 'cause we want to scan every bit(128, 64, 32, 16, 8, 4, 2, 1 - 8 bits).
work_byte++ - We get the next byte(next line of the bitmap).

Note: if you have no idea about BITS, visit here.
If you still don't understand it, you are a dumb(j/k) read the code a few more times and it will be clearer,
or I'm a bad teacher :(

void writestring(int x, int y, char *string) { for (int index = 0; string[index] != 0; index++) drawchar(x +(index << 3), y, string[index]); // We multpile the character position on the string by 8 in order to get it's position on the screen. } void writestring(int x, int y, int number) {//Same function, but here we just convert the number into a string and blits it. char string[6]; itoa(number, string, 10); for (int index = 0; string[index] != 0; index++) drawchar(x +(index << 3), y, string[index]); }