‫Hello and welcome.
‫In this lecture, we're going to discuss what tax code is, so what is tax code?
‫While tax code allows you to write ASCII to video memory, it supports 16 unique colors and there's
‫no need to set individual pixels to screen to make a certain character.
‫So what do I mean when I say tax code allows you to write ASCII to video memory while you write ASCII
‫characters starting at the address you XP eight zero zero zero for colored displays or for monochrome
‫displays.
‫Address Xbox B zero zero zero zero.
‫So each ASCII character we write to this memory has its pixel equivalent, output it to the monitor.
‫There's no need for us to reference some table and try an output character, a pixel by pixel.
‫We just write the ASCII ASCII value for a or whatever to the memory and in the video card does the rest.
‫So these are the supporting colors in text mode.
‫You can see it's rather limited.
‫We don't have a lot.
‫So as I've already said, there's no need for us to set individual screen pixels for printing characters.
‫When we're in text mode, we just get get the character a write it into video memory, then the video
‫camera system table and sets pixels for us.
‫There's no need for us to reference any table of our own.
‫So another thing to note, each character takes of two bytes.
‫So Bytes zero is ASCII character, for example, character A character B, character C byte one is a
‫color code.
‫The references are color table that I just shown you.
‫So let's say we want to set Rosero column zero zero zero.
‫Add to a character A that's black.
‫Then we do this by writing to address you x, B eight zero zero zero and we put A in there and then
‫in addressing X be a zero zero one we put zero zero zero, which references the color black in the color
‫table.
‫Right.
‫And then likewise if we want to then said Y zero and x1 or row zero column one to a black B so.
‫So character B this black then we just go zero B eight zero zero two unless equal debate and zero X
‫B eight zero zero three and that is equal to zero.
‫So if you're not familiar with the ASCII table, you need to go and learn it right now because we're
‫going to be actually implementing this in in the next lecture.
‫So you're going to need to learn that first.
‫And then we watched this presentation.