Questions tagged [design-choices]

Justifications and trade-offs of historical hardware and software designs, and their possible alternatives.

Filter by
Sorted by
Tagged with
6 votes
3 answers
1k views

What was the reason that the original Western NES console had a "cartridge bed" that had to be pushed down to play?

In Japan, they had the Famicom. You put in the cartridges on the top, just like with the later SNES and other consoles. But for Europe and the USA (and the entire "West"), the "NES"...
36 votes
8 answers
7k views

Did they forget to add the physical layout to the USB keyboard standard?

USB keyboards must have been one of the first devices that could be connected to a USB port. When you are from the US it's possible that you have never faced this problem. But in all other parts of ...
29 votes
5 answers
8k views

Why did old IBM-PC-compatible computers only have 16 colors available?

In the MS-DOS Editor, the only choices for colors were a collection of 16 colors: That's 16 colors: Black Blue Green Cyan Red Magenta Brown White Gray Bright Blue Bright Green Bright Cyan Bright Red ...
26 votes
5 answers
3k views

Why does the FAT file system have separate ‘hidden’ and ‘system’ attributes?

File systems used by DOS and Windows have used file attribute bits as a relatively prominent feature. The first of them, FAT, exposes four attributes to the user: read-only, archive, hidden and ...
12 votes
2 answers
650 views

Why does the FRE() function in CBM BASIC v2 return negative values?

On Commodore machines featuring CBM BASIC v2, the FRE() function to query the amount of memory available to BASIC returns a negative number when the result exceeds 32767 bytes: This quirk does not ...
24 votes
6 answers
3k views

Why didn’t the 1980s micros use MC68010?

These are all legendary 16/32-bit machines that were introduced in 1984 or later that are running the 68000: Apple Macintosh Atari ST Commodore Amiga Sharp X68000 But the 68010 was already available,...
21 votes
8 answers
6k views

Why were nested functions excluded from B and C?

I'm learning C and was curious as to why the language does not allow nested functions. From what I've read, the lack of nested functions seems to have been a simplification that was inherited from its ...
16 votes
2 answers
3k views

Why was there a need for separate I/O address space in addition to a memory address space already?

I was reading through PCI and PCIe configuration access mechanism in Chapter 3 (page 96) of PCIe System Architecture (Mindshare series). As a solution to prevent locking (in case of multiple threads) ...
26 votes
10 answers
6k views

Why did the original design of COM on Windows rely on the Registry?

In the early 1990s Microsoft introduced COM (Component Object Model) which was widely used in various programming environments including Visual Basic 5 & 6. Also known as ActiveX (or at least if ...
75 votes
4 answers
25k views

Why is Windows using CR+LF and Unix just LF when Unix is the older system?

Windows and MS-DOS use the control characters CR+LF (carriage return, line feed) for new lines, while Unix uses just LF. As far as I know CR+LF made sense for systems controlling a real teletypewriter,...
18 votes
5 answers
5k views

Why did old consoles have special RAM dedicated for a specific task?

Even in the PlayStation/Saturn era, they had like little RAM chips which were dedicated to just "sound", or "video", or "general". Since they still needed to have the RAM ...
8 votes
2 answers
931 views

Why did CGA RGBI output leave DAC to the monitor?

CGA on the original IBM PC produced sixteen colors, one bit each for red, green, blue and overall intensity modifier. The preferred output device was the later-arriving 5153 color monitor, which ...
34 votes
1 answer
11k views

Why did the NES not allow rotated sprites?

I'm taking a look at the chapter on sprites from a NES programming guide at famicom.party. There is a little table which describes what the different sprite attribute flags do: Bit # Purpose 7 Flips ...
55 votes
8 answers
11k views

Why didn't the 8086 use linear addressing?

The 8086 used a segmented memory architecture where the linear address was computed from a 16-bit segment number and a 16-bit offset. This greatly complicated things from a programming perspective. ...
24 votes
1 answer
2k views

Why was PETSCII based on an obsolete version of ASCII?

PETSCII (sometimes PETASCII) is the character set developed by Commodore for use in its microcomputers. The first of these, the PET, started to be developed in early 1976. Why, then, did Commodore ...
6 votes
1 answer
563 views

Why did the 8085 multiplex data with the low address byte?

Intel’s 8085 used bus multiplexing to stuff more functionality into 40 pins than would otherwise be possible. One of those pins, ALE, signals when the AD0…7 pins are outputting the low byte of the ...
9 votes
2 answers
2k views

Why did the BIOS load the MBR at 0x7c00?

The IVT is at 0x0000-0x03ff while the BDA is at 0x0400-0x04ff but boot sectors are loaded at 0x7c00. What was at 0x0500-0x7bff that caused this convention? I'm also curious why some MBRs relocate ...
19 votes
7 answers
5k views

Why does the x86 not have an instruction to obtain its instruction pointer?

This has always confused me. Why can you not directly obtain the IP, and instead have to go through some odd assembly hoops such as calling a function whose only purpose is to push its own return ...
28 votes
1 answer
3k views

When and why was the question mark chosen to abbreviate PRINT?

In many dialects of BASIC, the PRINT statement can be abbreviated with a single question mark when entering programs or direct-mode commands. So instead of typing PRINT "HELLO, WORLD" you ...
9 votes
1 answer
473 views

What is the purpose of the 2x4-bit split of the PCH incrementer?

On this detailed 6502 block diagram that can be found all over the net, the increment logic for the high byte of the program counter is split into two 4-bit parts, with a named PCHC line for the carry ...
36 votes
5 answers
11k 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 ...
9 votes
2 answers
1k views

What technical reasons prevented the Win9x Virtual Machine Monitor from running multiple threads simultaneously?

Were there any inherent limitations in the way the VMM for Win9x was designed that prevented it from being able to run threads simultaneously if the underlying hardware had multiple cores/processors? ...
28 votes
3 answers
4k views

The two types of Return keys on keyboard layouts

Why have these two types of Return keys persisted to this day? A quick look at different keyboards from different keyboard manufacturers from today shows the Shift-style Return seems to have more ...
8 votes
7 answers
2k views

Why are symmetric bi-directional communication port cables not always crossover cables?

There are a number of bi-directional communication port standards in which cables are used to connect two identical ports, and usually those connect each pin of one port to the same pin of the other ...
25 votes
5 answers
3k views

Why did the stock Amigas not have a battery for keeping the time/date?

The Amiga computers were advanced machines meant to do all sorts of things, including file management. They had a GUI OS (Workbench) and everything right from the very start. They were not some games-...
38 votes
3 answers
12k 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 ...
15 votes
2 answers
3k views

Why are the magnetic floppy disk drives (FDD) heads not frictionless?

After reading this answer to the question How long can a floppy disk spin before wearing out? ... one could see thru the floppy... Not just badly worn, but the magnetic coating was outright polished ...
21 votes
4 answers
8k views

Why are the Nintendo 64 memory cards' batteries *soldered* on?

After recently learning that it has a battery inside of it, I unscrewed my Controller Pak (N64 memory card) to put in a new battery. The old one says "98" on it, referring to 1998. So it's ...
10 votes
2 answers
2k views

How did the 6502 designers intend for the indirect addressing modes to be used?

The 6502 has three indirect addressing modes: Indirect, Indexed Indirect (Indirect,X) and Indirect Indexed (Indirect,Y). Indirect is only used on the JMP instruction, no other. Why was this mode ...
38 votes
6 answers
7k views

Why couldn't early C compilers handle variable declarations between statements?

In modern C, you may place variable declarations between statements: do_something(); int x; x = something_else(); However, older C compilers required that variables are declared before all statements:...
16 votes
3 answers
919 views

Why did instruction sets since the late 1970s seemingly stop including an "execute" instruction?

Many mainframe instruction set architectures (ISAs) in the 1960s included an Execute instruction, which would treat data as an instruction. I haven't found an architecture designed after 1976 which ...
6 votes
3 answers
673 views

What was the reasons for DEC engineers to choose MMU page size in VAXen?

MMU page size in VAXen is just 512 bytes. Such a small size causes increased number of MMU page walks and leads to TLB thrashing more often. Current tendency is to have MMU pages as big as 2 Mbytes. ...
26 votes
7 answers
5k views

Why do variable names in BASIC need type suffixes?

The BASIC I'm most familiar with is Atari BASIC since I had an Atari 800 way back when. The Atari BASIC Source Book includes details about how Atari BASIC maintains variables. There is a Variable Name ...
23 votes
8 answers
5k views

Why not constant linear velocity floppies?

The outer tracks of a disk are longer than the inner tracks, and could therefore potentially hold more data. Constant angular velocity puts the same number of bits on every track, which wastes much of ...
24 votes
2 answers
3k views

Was leaving all xxxxxx11 opcodes unused on the 6502 a deliberate design choice?

The 6502, like many 8-bit processors, has a somewhat arcane opcode-mode restrictions. On most such processors, the restriction is a clear result of trying to pack a lot of instructions into a limited ...
5 votes
1 answer
439 views

Why does the ‘Get Next Selector Increment Value’ DPMI call exist?

In DPMI, interrupt 0x31 services 0x0000 and 0x0100 are capable of simultaneously allocating multiple protected-mode selectors in a single call. When that happens, both services return only the first ...
4 votes
1 answer
386 views

Why did the Speak & Spell have an alphabetic keyboard?

Many of us remember the original Speak & Spell from 1978: Image source: Wikipedia One of the interesting things about this early handheld educational game console is the keyboard. It's not normal!...
3 votes
1 answer
830 views

Why were procedure parameter specifications optional in the ALGOL 60 Revised Report?

In Algol 60 procedure declarations, the 'specification' part was optional for by-name parameters. The specification is what gives (loosely speaking) the type of parameter - whether it's real, integer,...
16 votes
4 answers
3k views

Why does Pascal have numeric labels?

Pascal was intended, in part, to be a simple language to implement. Some of the design decisions reflecting this are Declarations/definitions must be given in a strict order (labels, constants, types,...
5 votes
0 answers
252 views

What was the first device to "beep" in lieu of tactile feedback to button presses?

I'm splitting this question off of When was beeping invented, in a user interface sense? because I think it's more answerable on its own and I suspect likely to still be computing-related. At some ...
6 votes
2 answers
648 views

When was beeping invented, in a user interface sense?

UPDATE: thanks all, lots of good discussion but I think this question is a bit too vague to be answerable. I'm casting my own close vote against it and will re-ask a more specific one. Specifically I ...
8 votes
1 answer
752 views

Were there any working computers using residue number systems?

Wikipedia says: A residue numeral system (RNS) is a numeral system representing integers by their values modulo several pairwise coprime integers called the moduli. Bit widths of each of those "...
52 votes
2 answers
24k views

Why were the /\ (min) and the \/ (max) operators abandoned in the C language?

In the UNIX V7 version of the C language (but not yet in the V6 version), there were the /\ (min) and the \/ (max) operators. In the source of the scanner part of the compiler, case BSLASH: if (...
107 votes
7 answers
26k views

Why was `!` chosen for negation?

It seems that the use of the exclamation mark ! to denote negation started with the C programming language (as far as I can tell from my Google research). Nowhere though is mentioned who and why chose ...
58 votes
8 answers
15k views

Could we have avoided the whole UTF-16 fiasco? [closed]

Anyone who has studied Unicode and is honest will admit that UTF-16 was kind of a mistake. It was born from the early assumption that 16 bits would be enough for all of Unicode. Then a hack was ...
59 votes
4 answers
11k views

Why were single quotes ('…') chosen for characters, and double quotes ("…") for strings?

In C, '' is used to denote a character, while "" is used to denote a string. Why was this syntax chosen? I tried to research this using Wikipedia’s Timeline of Programming Languages along ...
15 votes
2 answers
2k views

Why does the 6502 JSR instruction only increment the return address by 2 bytes?

Currently messing with 6502 assembly on a C64, and I don't understand why the JSR instruction is so weird. According to the instruction table, JSR is a 3-byte instruction and only operates in absolute ...
30 votes
8 answers
10k views

Why did post-8008 CPUs not keep the on-chip stack idea?

Ken Shirriff writes in his blog entry about the 8008: The 8008's seven registers are in the upper right. In the lower right is the address stack, which consists of eight 14-bit address words. ...
-4 votes
3 answers
355 views

What was the last personal computer to have the chips neatly arranged in rows and columns?

Once upon a time, the chips on the circuit boards of personal computers1 were arranged in a tidy grid pattern. Observe the board of the Apple ][+: Or the Commodore 128: Sadly, the zen of neat rows ...
75 votes
7 answers
13k views

Why wasn't ASCII designed with a contiguous alphanumeric character order?

Anyone who has dealt with strings at a low level (e.g., writing a parser in C), knows that doing so tends to involve frequent checks of—either manually, or through isalpha(), isalnum(), etc—whether a ...