[susam]

With aspect=1, the square is 400 pixels high and 384 pixels wide, not exactly an aspect ratio of 1:1 but quite close, 1.04:1.

The parent of my earlier comment, i.e., the one by klodolph, claims that the pixel aspect ratio would be square by default in DOSBox, so I thought I would verify it once. As per my experiments, that does not seem to be the case.

[klodolph]

This is a misinterpretation of the experiment results.

By default, aspect=false. This gives incorrect results, as you observed, with Logo producing a squashed circle and square.

The fix is aspect=true (or aspect=1). This gives correct results, with non-square aspect for pixels, with Logo producing a more correct circle and square.

Because the Logo implementation was written for an actual IBM PC or compatible, it assumes that the aspect ratio of a 320x200 pixel screen is about 4:3. However, when displayed with the incorrect square-pixel aspect ratio given by default in DOSBox, it will be 8:5.

In other words, DOSBox displays graphics with a square pixel ratio by default, which is different from the original hardware. If you wrote a DOS program to draw a square number of pixels, say 128x128, then you would see that in DOSBox it would also be square, but on real hardware it would be about 20% taller than it is wide. If you use Logo you will get the opposite results, because Logo is correctly designed for the original hardware.

[fireattack]

I think what he meant is that,

The pixels are square in DOSBox, but the graphics from these old programs are designed for non-square pixel ratio. So, if you display it with square pixel, the display aspect ratio will be wrong.

(Of course, this still contradicts with what neatcoder said, but I can't remember if these programs were "squished" on CRTs or not.)

[susam]

See these screenshots of SCREEN 2 in GW-BASIC running in DOSBox:

- https://imgur.com/NZUGL1e (aspect=0)

- https://imgur.com/rnQOfA4 (aspect=1)

The one with aspect=1 looks very odd.

[klodolph]

The one with aspect=1 looks incorrectly configured.

There are a number of different graphics modes, they have different pixel aspect ratios, you can also adjust the monitor, it is possible that back in school you were using a different mode or a different monitor. I think there are some other factors that can affect this.

[susam]

Back in school, I played with SCREEN 0, SCREEN 1, and SCREEN 2 documented in the GW-BASIC user manual. Here's a copy: http://www.antonis.de/qbebooks/gwbasman/screens.html .

The reason why I stick to aspect=0 (the DOSBox default) is that this is the one that more closely reproduces the experience I had with the CRT monitors at school. I agree that the actual monitor or the way it is configured could affect the aspect ratio we observe. Perhaps ours was not adjusted to produce 1:1 square while working with IBM Logo. But it did produce 1:1 square with GW-BASIC SCREEN 1 mode.

[klodolph]

CGA/EGA/VGA is supposed to have a pixel aspect ratio of 1:1.2 in 320x200 mode. If you adjusted the monitor to give 1:1 square pixels, then this was unusual.

[susam]

I think I know why the screenshot for SCREEN mode looks odd with aspect=1. The documentation at https://www.dosbox.com/wiki/Dosbox.conf mentions,

> Do aspect correction. It only affects non-square pixel modes like VGA Mode 13h, which has a resolution of 320x200 pixels and is used by many DOS games (DOOM, etc).

However SCREEN 2 mode of GW-BASIC has a resolution of 640x200 ( http://www.antonis.de/qbebooks/gwbasman/screens.html ).