It's pretty amazing to me that, if your goal is to check that the intern candidate can write plain C, the questions still look pretty reasonable to me even in 2026, maybe except for the question related to colors which will probably confuse the majority of the interns (2 bits per color? how is that possible).
For the circle drawing exercise, it just seems that the interviewer did not do a good job hinting the author. Fun fact: a person I know got this question on their Microsoft interview in around 2016. I guess, it the question works, why bother changing it!
this is probably a rhetorical question, but lemme answer anyways: By packing the colour channels into a single byte. So, for example, you'd have RRGGBBAA within a single byte, for each pixel. Giving you 64 possible colours, with 4 steps of alpha.
Or if you don't need to have alpha, you could pack it even further down to RRGGBB in a byte, which leaves 2 bits left over for the next pixel. Via that, you can pack four pixels worth of colour data into 3 bytes: RRGGBBRR|GGBBRRGG|BBRRGGBB (italics for delineting pixels, vertical bars for delineting bytes)
The latter is a tradeoff between compression and a more complex accessing pattern.
A bit of a tangent, some system used RRRGGGBB for colours, because the eyes are the least sensitive to differentiating the amount of blue, so that's another way to use up a full byte per pixel.
Oh right. Guess the " (2 bits per color? how is that possible)" is what threw me off there, because I read it as 2 bits per colour channel, rather than cga colour. Of course, "indexed" colours can get away with much fewer bits.
For the circle drawing exercise, it just seems that the interviewer did not do a good job hinting the author. Fun fact: a person I know got this question on their Microsoft interview in around 2016. I guess, it the question works, why bother changing it!
this is probably a rhetorical question, but lemme answer anyways: By packing the colour channels into a single byte. So, for example, you'd have RRGGBBAA within a single byte, for each pixel. Giving you 64 possible colours, with 4 steps of alpha.
Or if you don't need to have alpha, you could pack it even further down to RRGGBB in a byte, which leaves 2 bits left over for the next pixel. Via that, you can pack four pixels worth of colour data into 3 bytes: RRGGBBRR|GGBBRRGG|BBRRGGBB (italics for delineting pixels, vertical bars for delineting bytes)
The latter is a tradeoff between compression and a more complex accessing pattern.
A bit of a tangent, some system used RRRGGGBB for colours, because the eyes are the least sensitive to differentiating the amount of blue, so that's another way to use up a full byte per pixel.
https://en.wikipedia.org/wiki/Color_depth
But the original post actually talks about CGA [1] with just four colors. Encoding a color needs two bits then, so each byte encodes four pixels.
[1]: https://en.wikipedia.org/wiki/Color_Graphics_Adapter