Databases
StackOverflow2013
Postsdbo
POHow does a machine determine what is displayed on a screen (6502 specifically)?
 

Note that there are some explanatory texts on larger screens.

plurals
  1. POHow does a machine determine what is displayed on a screen (6502 specifically)?
    primarykey
    data
    text
    <p>I know this is an incredibly vague question, and it might not be a good question for programmers, since this is really a hardware related thing, but I guess some assembly/machinecode comes into play which would be appropriate for this site. </p> <p>So what I'm wondering is; imagine the 6502 processor. It has some registers, an instruction set, and access to a certain amount of memory. Then imagine that you have some LCD screen with an arbitrary resolution. How is it determined what is shown on this screen? How is it determined which pixels at which position is given what color? Does the screen always display, for instance, a pixel with the value in the accumulator of the 6502, and with x position stored in register x, and y position stored in y? Or is it interpreted differently by every machine? </p> <p>Someone wrote a JavaScript 6502 emulator, and the device displays a pixel with its value at some memory position starting with $200. So for instance: </p> <pre><code>LDA #$08 STA $200 </code></pre> <p>would display a pinkish pixel at position x:0, y:0. </p> <pre><code>LDA #$01 STA $205 </code></pre> <p>would display a white pixel at position x:5, y:0. </p> <p>If you look at the NES, however, it has a dedicated PPU which displays certain pixels with a certain value at a certain area on the screen. </p> <p>So how does it work? Is it interpreted differently by every machine (i.e. Apple II, C64, NES), or is there some kind of consistency of how it is interpreted? </p> <p>As a matter of fact, what would happen if a program compiled for an Apple II was somehow executed on a C64? The machine should be able to read the instructions, right? </p>
    singulars
    1. PO
      singulars
      1. PTAnswer
    1. This table or related slice is empty.
    1. PTQuestion
    1. USZimZim
    1. USZimZim
    plurals
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. This table or related slice is empty.
    1. PO
      singulars
      1. PTAnswer
    2. PO
      singulars
      1. PTAnswer
    3. PO
      singulars
      1. PTAnswer
    1. VO
      singulars
      1. POHow does a machine determine what is displayed on a screen (6502 specifically)?
      1. This table or related slice is empty.
      1. VTClose
    2. VO
      singulars
      1. POHow does a machine determine what is displayed on a screen (6502 specifically)?
      1. This table or related slice is empty.
      1. VTUpMod
    3. VO
      singulars
      1. POHow does a machine determine what is displayed on a screen (6502 specifically)?
      1. This table or related slice is empty.
      1. VTUpMod
    1. COThis is not a programming question, and even if it were it is not specific to assembly language or the 6502.
      singulars
      1. POHow does a machine determine what is displayed on a screen (6502 specifically)?
      1. USEight-Bit Guru
    2. COYes, I already stated that I was unaware whether this was an appropriate question or not, so I asked anyway because I thought a lot of programmers on this site would probably have some hardware knowledge on the side. I will keep in mind not to ask these kinds of questions in the future.
      singulars
      1. POHow does a machine determine what is displayed on a screen (6502 specifically)?
      1. USZimZim
    3. COI'm sure a lot of programmers on this site *do* have a great deal of hardware knowledge, but SO is all about programming; your question is inherently hardware-focused since converting memory structures into scanlines on a display is a system-specific hardware task (which is not to say that the question isn't interesting or valid, only that it doesn't belong here).
      singulars
      1. POHow does a machine determine what is displayed on a screen (6502 specifically)?
      1. USEight-Bit Guru
 

Querying!

 
Guidance
A row detail

Detail views are divided into sections. All the information in the data section comes from columns in the selected row. The other sections display data from other, related rows.

Related data can be related in a to-one or a to-many fashion. Captions of data related in a to-many fashion link to a list view showing a filtered view of the table.

Try moving around until you find a non-empty to-many entry and click on the label to get to one. You can move back to the root by clicking on the database name in the header.

SQuiL has stopped working due to an internal error.

If you are curious you may find further information in the browser console, which is accessible through the devtools (F12).

Reload