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1500 questions
20
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5 answers
What other computers used this floating-point format?
I have discovered that the DEC PDP-10 used a floating-point format that differed from IEEE-754 in an interesting way.
IEEE-754 is like sign-magnitude representation. The only difference between a positive value and its negative is the value of the…
robert bristow-johnson
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3 answers
Did mechanical hard drives often malfunction in high elevation places such as Bogota?
Bogota, Colombia has an elevation of 2,640m. A cable car in the city (Teleférico de Monserrate) can also take one to an elevation of 3,152m. Given that regular hard drives were usually pressurized to operate in elevations up to 3,000m, was there a…
JonathanReez
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Are any CP/M systems still in commercial use today?
I understand that there is a great deal of mainframe-era enterprise software that is still in active use, if not on the original hardware then in emulated environments. Its users keep it running because it still works for its intended use cases and…
Psychonaut
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2 answers
Which is the first version of DOS to support more than one reserved sector in a FAT file system?
I'm trying to fix a problem when trying to use DOS stuff on SSDs. The problem is sector alignment in an SSD is completely different from what DOS expects, and writes to FAT do funny things when the computer crashes in the middle that just don't…
Joshua
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What did the cassette bootloader in 8 Bit Ataris do?
...or for that matter, what didn't it do, so that you'd use the "bootloader/main program" separation instead of loading everything at once.
Normally, when loading games or any non-BASIC software from tapes, you'd start the computer holding…
SF.
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20
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4 answers
Who invented garbage collection?
Google tells me that John McCarthy invented garbage collection, for Lisp in 1959. However, a video on C that I was watching (‘Learn C Programming with Dr. Chuck’, c. 6:40) mentions the lack of a garbage collector and says that when Dennis Richie…
Neil Meyer
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20
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1 answer
When was the relocatable object module invented?
During the time when programming was done in machine codes, there was no need for object modules; it just wouldn't make sense. People would write the whole program they needed to run in "zeroes and ones", put it on a computer medium, and introduce…
Leo B.
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20
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3 answers
What exactly were those large orange chips on the Hayes Micromodem II interface card?
I've had a Hayes Micromodem II for the Apple ][ a very, very long time. I've seen a lot of interface cards over the years since then and have never seen anything quite like it: there are giant orange, bulbous chips on the board:
So my question is,…
bjb
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1 answer
In MS-DOS, how much stack do I need to make an int21 call?
The context is that I'm calling DOS interrupts from DPMI using int31 / ax=0x300, and you have to tell it what stack you want the real mode call to have. By default you get a small stack of about 20 bytes which isn't nearly enough. Experimentally…
David Given
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In 16-bit MS-DOS, how do I get a file handle to the currently running .exe?
The context is that I have additional data in the .exe file and wish to access it.
I know this is possible, as plenty of programs would store extra data after the loadable part of an MZ .exe — most 32-bit programs would do this; the 16-bit part…
David Given
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20
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4 answers
Does any computer resemble the model taught in UK secondary education?
In UK secondary education, there's a model called the fetch-execute cycle, which describes how computers work. (See: Isaac CS; Bitesize GCSE, Higher; Teach CS.) As I understand it:
The processor has at least one general-purpose register, usable as a…
wizzwizz4
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20
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6 answers
Where is DOS stored in memory when a program starts?
When the execution of a COM program begins, DOS jumps to address 100h. But at what address is DOS stored in RAM while the COM program is executing? Is DOS stored in conventional memory? If so, isn't there a risk that the COM program may overwrite…
Flux
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20
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8 answers
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 address onto the stack?
I'm asking about the…
Michael Stachowsky
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votes
6 answers
Does lossy audio compression damage datasette data?
I grew up with the C64 and had software on cassette tapes. These days, you can find "backups" of this software all over the internet, even in mp3 format (by recording the audio signal with a sound interface and converting it).
Since mp3 is lossy,…
Jeroen Jacobs
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4 answers
Can powering on/off a 1541 damage a disk left inside?
The User's Guide for the Commodore 1541 disk drive includes a vague warning, on page 7, to "remember to always remove the diskette before the drive is turned off or on". Some third-party books and magazines issue the same warning even more…
Psychonaut
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