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35
votes
4answers
9k views

Why do keyboards have an asterisk?

While we're all accustomed to using * as the multiplication symbol (not to mention other esoteric meanings in programming) it is of course not actually the everyday standard symbol for multiplication. ...
35
votes
16answers
10k views

Did anyone ever use the extra set of registers on the Z80?

The Z80 has the surprising feature of a second set of registers. I suppose these were intended to be used for rapid task switching or interrupt handling, though I think if I were programming a Z80 ...
35
votes
7answers
12k views

Why did Commodore 64 cartridge games disappear?

The Commodore 64 has a cartridge slot, but by the mid-eighties, cartridge games disappeared; everything was on tape or disk. Why? One answer that suggests itself is that by that time, a larger ...
35
votes
5answers
7k views

Why does the 6502 have the BIT instruction?

The 6502 has a bit instruction which copies two of the bits into the N and V flags, pretends to and the byte with the accumulator, but discards the result and only affects Z. I'm having a hard time ...
35
votes
10answers
8k views

Is there a reason to prefer earlier versions of MS-DOS over later?

I understand MS-DOS to be backwards-compatible, so is there a reason to run a version earlier than the last (6.22) on an old computer? The only reason I can think of would be for period-accuracy, but ...
35
votes
8answers
10k views

Why were floppy disks invented after hard disks?

For those of us who grew up with personal computers in the 1970's or 1980's, the experience was a very gradual migration from floppy disks to hard disks as the primary persistent storage. So, based on ...
35
votes
6answers
8k views

Why does the Cray 2 use 400 Hz power, and why generate that from motors?

This Cray sales brochure details on page 4 that the Cray-2 uses 400 Hz power, and generates this from motors. 400 Hz power from motor generators I'm not sure that in 1986, the state of the art ...
35
votes
8answers
10k views

Why do articles use the term “UART” instead of “serial port”?

I am learning about old computers, and I have found the following image from this article: They use the terms "UART" instead of "serial port" and "UART driver" instead of "serial port driver", I have ...
35
votes
6answers
5k views

Why is this gcd implementation from the 80s so complicated?

First of all, I hope this is the right place to post this question. I was looking through one of my dad's old programming books from the 80s, and at the back it has a list of utility functions, one of ...
35
votes
3answers
11k views

Were any of the books mentioned in this scene from the movie Hackers real?

In this scene from the 1995 movie Hackers, Cereal pulls out several books referred to by different colors of the "technicolor rainbow", including a "green one", "luscious orange", the "Pink Shirt book"...
35
votes
6answers
4k views

What was the purpose and history of the C64's special keys?

I never had a Commodore 64 but I've always been curious what the purpose and history of some of the special keys were. In particular: C= Run/Stop Clr/Home Restore I'm mostly used to the standard ...
35
votes
3answers
9k views

Why did 80×25 become the text monitor standard?

Prior to the 1981 release of the IBM PC, the VT105 (72×20 1971), VT52 (80×12 1974), and VT100 (80×25 1978) text terminals were used on many Unix machines and the PDP-11 (probably the most widely used ...
35
votes
3answers
10k views

Were the dungeons in Legend of Zelda designed to fit together?

As can be seen in the image below, the dungeons of Legend of Zelda fit quite well together. Were they designed to be, or is this just a coincidence? Does this make them easier to store, with the ...
35
votes
3answers
5k views

What was the point of Apple Pascal having its own file system?

Apple's UCSD Pascal for the Apple II used its own file system rather than the existing DOS 3.3 of the day. I'm not sure if it overlapped SOS at all, but regardless of timelines it seems that the ...
35
votes
5answers
4k views

Why did Super-VGA offer the 5:4 1280×1024 resolution?

Before the age of LCDs, PC displays almost always targeted 4:3 CRT displays. And indeed, VGA and most super-VGA modes had 4:3 aspect ratio resulting in square pixels - except the odd 5:4 1280×1024 ...
35
votes
4answers
8k views

Why didn't Apple sue Commodore over the Amiga's GUI?

Famously, in the late 1980's Apple sued Microsoft over the "look and feel" of Windows 2.x. The claim was that Windows breached Apple's copyright by being too similar to the Mac UI. Apple ultimately ...
35
votes
4answers
5k views

Are old versions of Windows at risk of modern malware attacks?

On my answer to a previous question (Can I run Windows 98 and games from the same era on an AMD Duron CPU?) I finished with a warning about using Windows 98 on the Internet, which received the ...
35
votes
2answers
3k views

What mid-1970s to mid-1980s home computers had their graphics characters added to Unicode 13?

The Unicode 13.0.0 release notes mention among the symbol additions: 214 graphic characters that provide compatibility with various home computers from the mid-1970s to the mid-1980s and with early ...
35
votes
2answers
3k views

Where and what was Haunt.bat? A game pre-loaded on a c1992 PC

This doesn't belong on the gaming SE, so I'm trying my luck here. I'm looking for any info I can get on an old game that I simply known as "Haunt.bat". Here is the back-story: In the mid 90's a ...
34
votes
10answers
14k views

Were there ever 12-, 24-, 48-, etc bit processors?

After seeing this question, I was struck with an intense curiosity to know: Were there ever processors with word sizes that aren't powers of two, specifically after the 8-bit byte became the industry ...
34
votes
14answers
8k views

What “unusual” syntax assembly languages are/were there?

This question may have the apparent form of a question soliciting a "list" answer, but I'm expecting the list to be very short, so please bear with me. What "unusual" syntax assembly languages are/...
34
votes
4answers
16k views

Who is credited for the creation of Assembly Language?

The C Programming Language was originally developed by Dennis Ritchie who also co-designed the Unix operating system with which development of the language was closely intertwined. Is there a ...
34
votes
5answers
8k views

Why (historically) include the number of arguments (argc) as a parameter of main?

A comment on this answer to a StackOverflow question made me curious. According the C99 standard, section 5.1.2.2.1: The function called at program startup is named main. The implementation ...
34
votes
5answers
9k views

Why is the clock frequency of the PS/2 keyboard protocol so high?

The PS/2 keyboard protocol allows the keyboard to generate a clock rate between 10 kHz and 16.7 kHz. At 11 bits per scancode, 10 kHz is a massive 909 scancodes per second. World-record holder Barbara ...
34
votes
6answers
9k views

Using DRAM as a camera sensor?

Back in the days when COMECON (RVHP) was cloning digital ICs usually the first wave of such ICs were in a ceramic package with a glass window (similar to EPROM) to check for bugs and stuff while used. ...
34
votes
4answers
6k views

What was the IBM PC cost saving for using the 8088 vs 8086?

The decision to use the 8088, a version of the 8086 with the data bus restricted to 8 bits, in the original IBM PC, seems strange on the face of it, certainly hurt performance and intuitively shouldn'...
34
votes
8answers
11k views

Why did some early computer designers eschew integers?

Several early computer designs regarded a 'word' as representing not an integer, with the bits having values 2^0, 2^1, 2^2, ..., but as representing a fixed-point fraction 2^-1, 2^-2, 2^-3, ... (For ...
34
votes
3answers
5k views

Why are first four x86 GPRs named in such unintuitive order?

On x86 the first four general-purpose registers are named AX, CX, DX, BX. It would be quite intuitive if their indices (those used in instruction encoding) were in alphabetical order, but instead of ...
34
votes
2answers
4k views

Why did the C64 have ← and ↑ as dedicated keys?

I've always wondered why the Commmodore 64 had discrete keys dedicated for the ← and ↑ symbols. If I remember correctly, they weren't used in BASIC at all, and were not very useful for drawing, ...
34
votes
5answers
3k views

Which ports are which on this Soviet ZX Spectrum clone?

Today I got my (first) Soviet ZX Spectrum clone. The person who sold it to me had inherited it and had no idea how it worked. It seems to be a home-made clone, rather than a factory-built one. See ...
34
votes
3answers
4k views

80286 can switch from real mode to protected mode - but why not back?

It's been a while, but I've read in a system programming book that you could switch your Intel 80286 CPU from the normal real mode to a more powerful protected mode. I clearly remember that they said ...
34
votes
3answers
2k views

Why does the C64's LIST command choke on REM statements with a Shift+L?

On the Commodore 64 and VIC-20, the LIST command will abort with a ?SYNTAX ERROR on any line that contains a REM statement with a Shift+L character. A minimal program triggering the error would look ...
34
votes
3answers
10k views

What modification is required from a PC floppy for use in Amiga?

Around the end of the time of Amiga popularity, obtaining a replacement Amiga floppy drive was a nuisance, while PC drives were ubiquitous and cheap. One could install a PC drive in Amiga after ...
34
votes
2answers
2k views

Can the two CPUs in a Commodore 128 run at the same time?

The Commodore 128 has two CPUs. One is some variant of the 6502, and the other is a Z80. One CPU is there for compatibility with the Commodore 64 and the other is there presumably to give basic ...
34
votes
1answer
2k views

What soviet computer used trinary bits?

Discussing 'non-standard byte sizes' with co-workers today, one mentioned hearing of soviet experiments with computers that used three-state bytes - and not just what is common today, 0, 1 and High ...
34
votes
2answers
2k views

What BBC Microcomputer features were requested specifically by BBC engineers?

When requirements for the BBC Microcomputer were developed as part of the BBC Computer Literacy Project, an outline specification was created by an independent consultant, the late John Coll. This ...
33
votes
7answers
10k views

Last computer not to use octets / 8-bit bytes

I am old enough to remember computers that were not octet oriented. E.g. the first that I used was an ICL 4120. It had 24 bit words which were, when necessary, divided into four 6-bit characters. ...
33
votes
6answers
11k views

Which was the first programming language that had data types?

Machine language (and Assembly language) don't have the concept of data types, so if you want to add an int and a float variables in Assembly, you have to use the appropriate Assembly instruction that ...
33
votes
5answers
7k views

Why was nil defined as a reserved word in Pascal?

In Pascal, nil (the pointer value to "nothing") is a reserved word. Why wasn't it simply a predefined identifier as true and false are, for example? This is stated in PASCAL User Manual and Report p....
33
votes
8answers
6k views

How to put a delay in AUTOEXEC.BAT

I have this MS-DOS 6.22 machine which maps a network drive to a SAMBA share on a Raspberry PI. The PI is powered by a USB lead from the DOS machine, so the two power up together. The mapping starts ...
33
votes
6answers
3k views

How did Elite (BBC Micro) compress resources?

Elite, an Acornsoft game for the BBC Micro, is a game set in space. Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is.     — Douglas Adams There are a ...
33
votes
2answers
5k views

Can an x86 CPU running in real mode be considered to be basically an 8086 CPU?

When an x86 CPU is running in real mode, can it be considered to be basically an 8086 CPU (or maybe 8088)? Or are there differences between the two?
33
votes
6answers
7k views

Why do hard drives not use larger platter sizes anymore?

In reading a related question about floppy drive capacity, I thought to ask a question I've had for a long time. When I started programming, all PC hard drives used the 5¼" platter size. There were ...
33
votes
2answers
5k views

Why was UNIX never backported to the PDP-7?

Originally, UNIX was written in PDP-7 assembly, and then in PDP-11 assembly, but then when UNIX V4 began to be re-written in C in 1973 and was run mostly on the PDP-11. So far as I can tell, there ...
33
votes
1answer
9k views

Is it true that Netscape Navigator eventually became Mozilla Firefox?

Is it really the case that Mozilla Firefox is a modern day version of Netscape Navigator?
33
votes
3answers
4k views

How did Windows ME “cripple” DOS?

Windows ME includes the ability to create a bootable DOS floppy. This floppy contains versions of COMMAND.COM and IO.SYS that are "crippled" to remove real mode. This is done with only one changed ...
33
votes
2answers
9k views

On what computer did “JUMP” mean “don't jump?”

This question triggered a brain cell. I remember a computer architecture, possibly one that was known for its beautifully symmetric instruction set, with an assortment of distinct mnemonics for ...
33
votes
6answers
5k views

How do I Interface a PS/2 Keyboard without Modern Techniques?

I'm attempting to build a Z80 homebrew computer to teach myself the basis of electronic design. I planned to start from something simple, like a ROM, some SRAM, a video chip and a Z80-PIO. I'd like to ...
33
votes
3answers
4k views

Reconditioning and cleaning old Nintendo (and other) game cartridges

I used to blow the dust out of the cartridges but I heard that can actually damage the cartridge or the system itself. I am looking for the proper way to clean old Nintendo game cartridges (such as ...
33
votes
1answer
6k views

What do the keys on this Symbolics Space Cadet keyboard do?

Old keyboards like the one below seem to have contributed a lot to the design of modern keyboards. So, obviously, some of the keys are familiar because they are on my own average (modern Windows and ...

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