All Questions

154
votes
3answers
39k views

What algorithm did Microsoft use to dither colour in early versions of Windows?

In the late 1980s to mid 1990s, most consumer-class video hardware was not capable of displaying greater than 16 colours at a time. To create the illusion of greater colour, software often "blended" ...
101
votes
4answers
21k views

It's now safe to turn off your computer

One thing I remember very well from my childhood is the screen you got at the end of a shutdown process ond old computers: I don't know if this was a Windows 95/98/2000/ME only thing but I wonder why ...
99
votes
2answers
17k views

How did Commodore's anti-Microsoft Easter Egg work?

A couple years ago the Toronto PET Users Group published an article (The Great Commodore/Microsoft Easter Egg War, on p. 7) about a newly discovered anti-Microsoft Easter Egg that Commodore hid in the ...
93
votes
21answers
33k views

Was there ever any reason to wait 30 seconds to restart a c.1995 PC?

I owned a PC in the mid-to-late 90s, and while everyone said when you turn it off and back on again, count to 30. But it also had an instant reset button down below. Was there ever really any risk ...
89
votes
5answers
19k views

How can tilting a N64 cartridge cause such subtle glitches?

When the N64 cartridge is tilted in Super Mario 64, it reliably produces glitches such as this. Mario's limbs disappear, he rotates 90° and sinks into the floor, and the music gets messed up (usually ...
88
votes
16answers
20k views

Does “Disk Operating System” imply that there was a “non-disk” Operating System?

In the 1980's at primary school we saw MS DOS and DR DOS competing before Windows 3.1 and subsequent releases took over that space. At home we had Apple II's which booted up to a BASIC prompt. On ...
87
votes
16answers
21k views

How was early randomness generated?

Many programs make use of randomness, from BASIC guess-the-number games to encryption key generators. This randomness could have been generated in many, many different ways: hardware, software, ...
79
votes
7answers
26k views

Why would a NES game use an undocumented 1-byte or 2-byte NOP in production?

Reading the NESdev wiki page on CPU unofficial opcodes, I see a few games use an undocumented 2-byte NOP instuction in production: Puzznic, F-117A Stealth Fighter, and Infiltrator use $89 #i. Beauty ...
77
votes
4answers
7k views

Were there 8086 coprocessors other than the 8087?

The 8087 math coprocessor for the 8086 (and descendants) nominally added floating point and transcendental (trigonometric and logarithmic) instructions to the 8086. Contrary to naive expectations, the ...
74
votes
14answers
14k views

How did people use ed?

ed was the standard Unix editor, and is present on all POSIX certified systems (though it's not installed by default in Debian, FWIW). It's a line editor (meaning, you can't see all the text at a ...
74
votes
9answers
12k views

Why were CLIs typically light text on dark background, whereas GUIs typically use(d) dark text on light background?

My experience is that CLIs were typically shown with light text on a darker background. For example, the IBM PC would use white/light gray (depending on your point of view), amber or green (the latter ...
73
votes
18answers
15k views

Why was BASIC built into so many operating systems?

There are a lot of retro-computers with BASIC as an integral part of the operating system. The IBM 5100 was one of the first computers with a separate memory space for BASIC, followed by the Commodore ...
69
votes
8answers
8k views

What key factor led to the sudden commercial success of MS Windows with v3.0?

Microsoft Windows was originally introduced in 1985, ostensibly to compete with the Apple Macintosh, and other computers shipping with graphical shells by that time. However, early versions of Windows ...
67
votes
2answers
14k views

Why does the Minus World exist?

In Super Mario Bros. for the NES and Famicom there exists a secret world, accessible by clipping through a wall to the first warp zone and entering the left-most pipe. This pipe will take you to ...
66
votes
13answers
15k views

Did any 8-bit computer system / OS have concepts for concurrency and multitasking like we know from today?

So, today all major OS support multitasking and concurrency in languages like for instance threading. The Amiga seems to be the first home computer which has advanced concepts in this area. But had ...
66
votes
6answers
7k views

What technological factors drove the rise of “high-speed” modems in the early 1990s?

The first inexpensive modem I ever purchased was a 300 baud direct-connect unit for the C64 User Port in late 1983. I recall that a couple of years later (1986), 1200 baud modems were affordable and I ...
65
votes
2answers
10k views

How did Windows 3.1 implement multitasking?

Windows in its earliest days was simply a shell that ran on top of MS-DOS, which means that Windows 3.1 itself was actually just a standard MS-DOS application like any other. Yet, MS-DOS is not a ...
62
votes
10answers
13k views

How was C ported to architectures that had no hardware stack?

Thinking about machines such as the PDP-7, PDP-10, CDC-160 and so on1, these are machines which do not have a stack pointer which can quickly and easily change to point to a new stack frame, like the ...
60
votes
3answers
11k views

What character is the MS-DOS cursor?

The cursor used on my 486 (and Pentium 3) in MS-DOS 6/7 has a thick underlined character. I cannot find that in code page 437. The underscore character is the closest to it, but is thinner. Where ...
60
votes
2answers
7k views

Why did Unix use slash as the directory separator?

The Unix designers came from the GE/MIT Multics project, and Multics inspired some Unix features. In particular, Multics has a hierarchical filesystem, and so does Unix. On Multics, pathnames were of ...
59
votes
8answers
14k views

Why do C to Z80 compilers produce poor code?

When reading some other questions about compiling C for the Z80, How much benefit should be expected on a more advanced compiler for z80/r800 based computers? Native C compiler for Sinclair ZX ...
59
votes
11answers
16k views

Did Apple not originally allow anyone to develop software for the Macintosh?

This probably nearly belongs on Skeptics.SE but here goes. Within the last few years I've become an Apple convert for the most part, which occasionally brings me into (usually) good natured conflict ...
59
votes
7answers
13k views

Where did the popularity of the `i` variable come from?

I have heard that the reason the i variable is used so much is because there was an old computer where each variable could only be a single letter and that reserved the variables a through h as ...
58
votes
8answers
19k views

How was copying prevented when the first CD-ROM games were introduced?

Several ways exist to protect against the copying of games but, when CD-ROM games were first introduced, were there any measures taken by video game developers to prevent the copying of games?
58
votes
5answers
13k views

Is it safe to turn on a 40-year old TRS-80?

My father is a retired programmer. When I was in high school in the late 1970s, he purchased a TRS-80 model 1 (on which I learned to program in BASIC). At some point in the early 1980s it, together ...
57
votes
13answers
13k views

Were later MS-DOS versions still implemented in x86 assembly?

Recently, Microsoft published the source code of old MS-DOS versions on GitHub. What is odd in my opinion is the use of x86 assembly language for everything. The assembly language would not be my ...
56
votes
13answers
19k views

Why did some early CPUs use external math chips?

While enjoying the response to "Why did CPU designers in the 70s prioritize reducing pin count?" In 1979 IEEE was hard at work at coming up with a standard for handling floating point numbers, and ...
56
votes
2answers
8k views

Why are a lot of monochrome computer monitors green?

In my perception, the most common color for monochrome computer monitors is green or white/grey, though I have seen orange monitors. Is this genuinely the case, and if so, is there a reason for it?
54
votes
2answers
7k views

What are the software logos in MORICONS.DLL?

Every copy of Windows comes with a file named MORICONS.DLL which was first distributed with Windows 3.0. As far as I know, this file has not been changed since Windows 3.0. Some of the icons include: ...
54
votes
6answers
6k views

Reason for the Amiga clock speed

The Amiga used a CPU rated for 8 megahertz, but clocked at 7.14 megahertz. What was the reason for this number? I remember it was something to do with a multiple of the frequency of the video ...
53
votes
3answers
10k views

Why did DOS use dollar-terminated strings?

According to a few tutorials I am seeing, DOS used dollar-terminated strings to write to the terminal. This seems to also be documented here on INT 21H. AH = 09h - WRITE STRING TO STANDARD OUTPUT ...
52
votes
7answers
11k views

Why use static RAM addresses instead of the stack?

I'm studying the 65c816 assembly for the 1994 game, Super Metroid. A hobbyist studied the game in-depth and created a RAM map. From it: 7E:0B56 - 7E:0B57 Moves Samus this distance horizontally, ...
51
votes
6answers
12k views

How were the first ZX Spectrum games written?

Being a child of the 80s I loved my ZX Spectrum, did my best to learn BASIC but I felt like the games I was playing (Jetpac, Dizzy, Renegade etc) were perhaps not written using BASIC. I wondered: how ...
51
votes
1answer
9k views

What's the story behind the name “X11”?

To this day on Linux configs and startup scripts for the GUI system are stored in /etc/X11. I remember this name appearing alone, or alongside others - XFree86, X.org, X - for as long as I had contact ...
50
votes
12answers
11k views

What early home computers have more than one CPU, where both could be used by the programmer? [closed]

I am interested to know if any computers that are on-topic for this site had more than one CPU, where this plurality could be leveraged by a programmer. Some cases I don't so much care about: The ...
50
votes
3answers
5k views

How does the LOADALL instruction on the 80286 work?

This undocumented instruction existed in the 80286 and, I believe, the 80386. I think it was added while debugging the chip, so the engineers could quickly put the processor into any state and test it ...
48
votes
18answers
8k views

Have programming languages driven hardware development?

Programming language development has been influenced by hardware design. One example from this answer mentions how C pointers were, at least in part, influenced by the design of the PDP-11. Has the ...
48
votes
12answers
11k views

How was the first assembler for a new home computer platform written?

How did the 8-bit computers (Spectrum, Commodore, Atari, Amstrad etc) typically "bootstrap" from bare electronics into a platform with a working assembly language and OS? What I mean: An assembler is ...
48
votes
5answers
9k views

Why did base64 win against uuencode?

From the the two methods of encoding 8-bit data as human-readable ASCII, for a time, uuencode format was more popular. USENET 'binaries' groups were filled with uuencoded posts with whatever goodies ...
47
votes
19answers
11k views

Did personal computers ever support 8" floppies?

When I look at the following picture, it seems a bit awkward to me that personal computers ever supported 8" floppies (unless the size of your computer case was as big as a fridge !): Am I right or ...
47
votes
2answers
9k views

Why did Commodore fill their power supplies with epoxy?

If you know anything about the Commodore 64 (and other Commodores, really) you know that Commodore really went the cheap route and produced some awful power supplies. The Commodore 128 PSU isn't ...
47
votes
3answers
6k views

What was Nintendo's Software Development Environment for NES Games?

(This question was inspired by my previous question What kind of software was used to develop Nintendo 64 titles?) The NES used a modified 6502 processor and most games were written in Assembly. ...
46
votes
11answers
13k views

Why did trackballs disappear?

For a desktop computer, a mouse is a great pointing device. For a laptop if you don't want an extra device to keep track of, you need an alternative. The options I'm aware of: NubLow-tech, cheap, ...
46
votes
8answers
5k views

How were Western computer chips reverse-engineered in USSR?

The British ZX Spectrum computer had many clones in the Eastern Bloc. It seems many of them were built using Russian-made chips from the Angstrem factory in Zelenograd in/near Moscow. The Russian ...
46
votes
5answers
8k views

Which Linux or BSD distributions do still support i386, i486 or i586 CPUs?

Unfortunately Debian kicked out Pentium 1 (i586) CPU support from its 32-bit PC port (named i386 for historic circumstances) for its next stable release Debian 9 Stretch. (Then again they complain ...
46
votes
4answers
2k views

Why do older computer cases turn yellow?

Why do plastic cases of old computers turn yellow? Is this yellowing a problem that has been solved in modern plastics?
45
votes
4answers
8k views

Why did F1 become the Help Key?

There was actually a pretty big push among some vendors in the 1980's to have a dedicated Help Key (conveniently labeled as Help). Atari introduced it in 1983, and kept it to the end. The Commodore ...
45
votes
1answer
19k views

How exactly does Sonic & Knuckles' 'Lock-On Technology' work?

The cartridge of Sonic & Knuckles is a little special: It flips open to allow you to connect another Sega Mega Drive (Genesis in US) cartridge to the top of it like so: I know why the Sega ...
44
votes
11answers
16k views

Why not use fractions instead of floating point?

Considering all those early home computers, the ZX Spectrum, the Galaksija, the VIC-20, the Apple I/II/III, and all of those, they all have some 8-bit CPU which does integer arithmetic and no floating ...
44
votes
10answers
7k views

Why was preemptive multitasking so slow in coming to consumer OS's?

Preemptive (rather than cooperative) multitasking was a highly-touted feature for PC's in 1996, with its inclusion in Windows 95 for the first time. It was also highly-touted for 2001 Macs when ...

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