C. J., Official discussed on TechStuff
Describing. This technology will also require us to examine a couple of other sets of standards that affected the graphics that displayed on old. Cg Systems C. J. had big limitations heck compared to graphics cards today. They seem absolutely stone-age the CJ system could support for different modes officially but clever programmers figured out ways to boost. This will get into that. There were two text the modes and too graphic modes for the CGI card. The I text mode supported four bit color and could display up to forty characters per line with twenty five lines making up the total screen space. So twenty-five like you could stack vertically or you could stack forty horizontally across the screen the Pixel aspect ratio. One to one point two. But what does that mean? Well these pixels are not perfect squares. They were actually taller than they were wide with that ratio of one for width to one point two for height this would mean that the visual resolution of the screen was more like three twenty by two forty in actuality it was three twenty by two hundred so why the three twenty by to forty well because the pixels were longer than they were wide. If you were clever with the way you create your computer graphics it would seem almost like you had stacked more pixels vertically and you could take advantage of things and make a picture that had that sort of look as if it was a resolution of three twenty by to forty however if you needed to cut things short and the ratio just wasn't working for you it would become a detriment not an asset. However if you do the math you'll see that this means every character onscreen with eight pixels dedicated to it. And here's how I did that. You just take the resolution with. That's three twenty pixels. You divide that by the number of characters that could fit on one line for merits forty characters across so three twenty divided by forty. You get eight. The same is true vertically. You can have twenty-five characters stacked from top to bottom on the screen and the vertical resolution is two hundred pixels top to bottom two hundred divided by twenty-five so each character and the adapter supported two hundred and fifty six different characters could use eight pixels for display purposes. The four bit color part also needs explaining so a bit is a single unit of computer information and we represented as either a zero or a one so that means a bit has one of two possible states. At any given time you can think of it as off or on zero or one. We have four bits for four bit color so that means we can think of having to the possible number of states per bit raised to the power of four. That's equal to sixteen so forbid color could support sixteen different colors total not all at once but total like that's the number of colors. The display could show in text mode. Programmers could choose a foreground and background color choosing from those sixteen premade colors. In addition a bit for the foreground color could be dedicated to make the character blink. So you can have blinking text in the foreground. The blinking bit. The bit responsible for that blinking. Command was re purposed for the background color. And it's served as an intensity bit instead. Intensity essentially means how dark or bright. That particular color happens to appear. The second text mode was an eighty by twenty five four. Bit Color Mode. So that meant you could fit eighty letters across in a line. Twenty five lines per screen. These letters were half as wide as the forty by twenty-five versions. Make sense right. You can fit twice as many across the screen. They must be half as wide as the forty by twenty-five the pixel ratio that this would create for a visual representation of the resolution was six forty by four eighty now in reality. Those pixels again were taller than they were wide. In fact they were notably taller than they were wide so the real resolution the true resolution with six forty by two hundred but like six forty by four eighty more programs were written in this mode because that you could fit way more taxed on a screen than you could with the forty by twenty-five mode it was less chunky but most text based programs relied on the eighty twenty five approach. If you're using a word processor or something. This was the style that you were most likely looking at that being said the resolution of taxed on a CJ machine was lower than what you would have found on the monochromatic MDA computers so there was a trade off you could have a CG IBM PC running on this eighty by twenty five text mode for a specific program. And it'd be fine. It just wouldn't be as crisp and clear as the monochromatic. Mda text specific machines onto the graphics modes. However that's what we're really interested in right. What actually made the images not just the text on these computers well the graphics mode for CJ machine had like I said two different modes to two different official modes to it was a three twenty by two hundred resolution. But the Pixel ratio was one to one point two so again. It looked more like three twenty by two forty. This mode could display up to four colors at any one time using one of two pre-selected Pallets. This is why if you ever look at old. Cgi Games they all start to look really similar. They're all using the exact same colors. Four colors the program is working under some really tight restrictions. The first Palette of colors included black green red and yellow. This was Palette Zero. The second pallet a pellet one had black Cihan Magenta and white now as you can imagine this pretty tough to create good graphics with this limited color selection now on top of that programmers could use low intensity or brightness or high intensity or brightness so that would add another variation and I've seen the same screen presented in both pallets at both levels of intensity and there are differences. Like you can get very different effect. Going from one to the other. So programs had a little bit of flexibility but not by much in both pallets. Black is color zero and color. Zero was actually customizable. You could swap it out. You could choose one of the other fifteen colors that CJ supported and use that as color zero black would no longer be used the flip side of this. Is that the new color. Would replace color zero in all of the image. So if you wanted the image to have black in it it would get replaced by whatever color you had now designated as color zero if you wanted to have green included with your white cyanogen and Magenta. Then it would mean that if you had a scene with the night sky that night skies going to be green because it would normally be black but you've designated that colored to go to green instead of black so yeah very limited however another trick. Programmers could do is leverage the way. Crt screens work. I'm going to gloss over the details but in CRT screens there is an electron gun and it paints the back of the screen with electrons. That causes fostered the glow as the phosphorus ABS electrons. But the painting is the important part. It happens at the top line. On the screen. It goes all the way across horizontally. Then it moves down a line and it does this again and it..