What does 1024x768X24 mean?

I was planning to change the Plymouth screen resolution(Blame Fglrx!).

When I went to GRUB-Customizer(info for that), the screen resolution menu shows (as usual) 800x600, 1024x678, 600x400, and a bunch of other things.

But after I scrolled down, I saw weird screen resolutions like 1024x768 x8, 1280x1024 x16, 800x600 x24, etc. Computer screens shape like a rectangle, not a cube, so what does those extra numbers mean? Or is there a secret dimension in every computer screen that I ignored?

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It relates to the number of colors simultaneously shown

That "third dimension" is the bit-depth, or how many colors can be displayed simultaneously on the screen at that resolution.

• x8 = 8 bits or 256 colors
• x16 = 16 bits or 65536 colors (also called "65k" or "high color")
• x24 = 24 bits or 16777216 colors (also called "16.7 million" or "true color")
• x32 = 32 bits or 4294967296 colors, or sometimes the same as 24-bits with 8 bits used for opacity/transparency (called "alpha")

Which should I choose?

The highest available. On most modern systems, that will be 24- or 32-bits. See the example below for why:

Example

• 24-bit

• 8-bit

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1 more question: How did you add the dots beside each row? – Emerson Hsieh Jun 2 '12 at 20:04
just begin with a `-`, and leave a space to make it a bullet point. – izx Jun 2 '12 at 20:06
Note that when it comes to overall display colour depth, "24 bit" and "32 bit" are often used interchangeably, but both really mean 24 bits are dedicated to colour information. It doesn't make sense to have an "alpha channel" in this context. Why call it 32 bits then? Probably just for programming reasons - 32 is the smallest power of two unit of memory that can be used to store a 24 bit data sample. – thomasrutter Jun 21 '12 at 1:46

The third number is the color depth. `1024x768X24` means 1024x768 pixels with a color depth of 24 bits. 8 bit will give you a Windows 95 color scheme, 16 bit will give you a much wider range of colors. 24 bit will give you millions of colors.

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x24 stands for 24 bits equally distributed in RGB constituents.

R:0-255 : 8 bits

G:0-255 : 8 bits

B:0-255 : 8 bits

Hence in this format the number of pixels of different color possible is 2^24

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