Many DOS functions use white textual content on a blue background because the default colours. Why is that this the default colour alternative? The reply, like so many issues in know-how, is due to its historical past. You’ll typically discover this similar colour scheme on many Home windows and Linux functions that run in character mode.
To grasp why functions adopted white-on-blue, it helps to first recall how DOS functions displayed textual content on the display screen. An ever-present DOS software was the phrase processor. WordStar, WordPerfect, PC-Write, and different phrase processors had been the mainstay of workplace computing within the Nineteen Eighties and Nineties. Whichever phrase processor you most well-liked, you in all probability used the default colours: both white textual content on a black background, or white textual content on a blue background.
However you may ask, “For those who’re modifying textual content that will later be printed on paper, why not present your doc in black textual content on a white background?” To reply that, let’s take into account DOS textual content.
DOS textual content was character solely. You can change the colour, however you couldn’t modify the fashion. There was no daring, italics, and underline “font” in plain textual content mode. And for extra advanced paperwork, you didn’t have a separate textual content fashion for hyperlinks or footnotes. In character mode, the PC may solely show plain textual content. You can change the textual content colour and background colour, and that was about it.
To get round this limitation, DOS functions used colours rather than display screen formatting. Let’s say your phrase processor used white textual content on a black background. You may see daring textual content in a vivid white colour, italics textual content in cyan, underlined textual content in inexperienced, or different textual content kinds in numerous colours:
This textual content is straightforward to learn. It is best to be capable to distinguish the totally different textual content kinds, and see the totally different textual content colours towards the primary physique textual content.
However studying white-on-black could be very tiring, so many functions adopted a extra in style colour scheme of white textual content on a blue background:
Even with the identical colours for every of the textual content kinds, you may nonetheless simply establish the totally different kinds used on this pattern. The intense white stands out as daring, the cyan and inexperienced establish italics and underlined textual content.
If we alter the colours to attempt to signify textual content as it would seem on a printed web page, with black textual content on a white background, we first run into the limitation that background colours can solely use the “low depth” colours. For instance, a normal PC show can not present textual content with a vivid white background. Utilizing the identical “fashion” colours from above, black textual content on a white background seems to be like this:
However what in the event you wished to show daring textual content in black? Assuming plain black for the textual content colour, you want a special textual content colour to signify daring. There isn’t a darker colour of black to signify daring textual content, so that you may as an alternative change daring to make use of the “vivid black” colour. This makes the daring textual content tougher to learn towards the white background:
And it will get worse in the event you attempt to set the textual content colour to “vivid black” and show daring textual content in plain black. The daring textual content is straightforward to learn, however the physique textual content fades into the white background:
The screenshots don’t fully signify how customers noticed textual content of their DOS functions. Computer systems of the period used CRT shows. These had been decrease decision than in the present day’s LCD shows. The place a contemporary show may help 1920×1080 pixels, commonplace VGA shows supported solely 640×480 resolutions.
I can approximate this decrease decision by graphics software program. (I used GIMP on Linux.) I’ve added a really gentle “bloom” to every of the screenshots, to simulate the CRT’s tendency to indicate lighter areas with a slight glow. I’ve additionally simulated a video degradation, consultant of displaying textual content on a lower-resolution monitor.
Viewing the screenshots with these distortions, you may see how white textual content on a black background supplied one of the best readability on a VGA monitor of the day. Right here, the gentle glow that was typical of DOS textual content on a CRT monitor truly helps make textual content simpler to learn:
The extra in style white textual content on a blue background additionally affords nice readability. You’ll be able to clearly distinguish the totally different textual content kinds. Even the brilliant white colour for daring stays seen towards the blue background. Scaling these photographs for the web site provides a slight artifact with the background “scan strains” – so this is likely to be extra consultant of a low-cost VGA monitor:
This additionally demonstrates why utilizing black textual content on a white background isn’t an important resolution for DOS phrase processing. The CRT provides a gentle glow round brighter areas on the display screen, inflicting black textual content on the white background to seem dim:
The textual content turns into more and more troublesome to learn in the event you change the daring textual content to make use of a “vivid black” colour, or in the event you change the physique textual content to make use of “vivid black” with plain black for daring. The textual content fades into the background, making the textual content troublesome to learn:
And that’s why most DOS functions used white textual content on a blue background. When you think about that DOS textual content solely had one “font,” and issue within the restricted colour set with sixteen textual content colours and eight background colours, utilizing white-on-blue or white-on-black made functions simpler to learn. Many functions began out with plain white textual content on a black background, however added colour when CGA, EGA, and VGA grew to become the norm in workplaces. The additional contact of colour, even only a blue background, made the functions really feel a bit extra trendy.
The subsequent time you see a DOS software, or perhaps a Home windows console software operating in textual content mode, keep in mind the colours. That’s why white-on-blue is so prevalent.