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recently i started studying computer science and computer graphics, and one question really haunts me. Mby someone can explain this. How bit patterns become translated into (for example ) text. I know we have encoding like ascii and unicode but this is also just bit patterns. Main mystery is at what point do the bits turn into what we see on the screen? So maybe you have some sources which can explain it? How bits translated into text?

ThanksBasic text which displayed on pc screen

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  • $\begingroup$ For what machine are we talking about? Because it's obviously different for old non-graphical CRT-based display systems than it is for modern computers. $\endgroup$ Feb 14, 2022 at 14:30
  • $\begingroup$ @NicolBolas , didn't know there is a difference, interesting to know about both $\endgroup$ Feb 14, 2022 at 15:14
  • $\begingroup$ You say that as though there are only two solutions. $\endgroup$ Feb 14, 2022 at 16:20
  • $\begingroup$ Its not easy to answer this question in the format of stackexhange, without a lot of hand-waving. With a lot of hand-waving the answer gets meaningless. Anyway how it is done depends entirely on the computer architecture and operating system. $\endgroup$
    – joojaa
    Feb 17, 2022 at 6:55
  • $\begingroup$ I have to recommend this video for how video hardware works. For CGA's there are character lookup tables (built in bitmap fonts) and tables. For modern computers, the CPU/GPU will render text as a bitmap. You can look up "Harfbuzz" to see how a modern font is turned into a bitmap by a CPU. $\endgroup$
    – Wyck
    Feb 18, 2022 at 17:14

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For a machine like in your image, the IBM PC, the characters shown are created using character ROMs. When software writes the character code into video memory, the memory hardware will use this code to lookup the bitmap from the character ROM.

This is very different from more modern home computers with a graphical windowing environment. Here the glyphs for characters are stored in font files. Some fonts do contain bitmaps, even the exact same ones from old character ROMs. But many fonts will contain a vector description of the glyph which has to be rastered into a bitmap before use.

Also, the importance of ascii is not to be underestimated. This was a monumental effort to standardize character encoding in a time when every computer in the world (pretty much) used a different code.

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I am not an expert in the area, but you can literally search for "bits into graphics" on google and get the following article. http://www.impacttectonics.org/GEO310/Labs/1B-Bits_and_Bytes.pdf which gives you a good description on how this work.

So essentially once you have access to the monitor, you get access to the array of pixel that monitor has.

Internally each pixel is a byte usually represented by 3 bytes Red, Green and Blue.

Then you just create your own font (text) with that information, and if you want. ASCII is was created to everyone knows what the value 65 (01000001) will represent when interacting with the computer.

I might be missing a lot of more information here, but I believe that's a good reference.

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  • $\begingroup$ Hi, Blad. Welcome to the site. I think this pdf is good information but it doesn't quite answer what OP was getting at. I think my explanation probably doesn't really get into the fun details like shift registers and the astonishing fact that the earliest CRTs were used for storage instead of display (google "the manchester machine"). I didn't downvote, but I think that may be the reason for it. This is not a bad post. But it's not a great answer to this question. $\endgroup$
    – luser droog
    Feb 20, 2022 at 6:12

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