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34
votes
4 answers
How widely was 0xDEADBEEF used as a placeholder, invalid value?
Inspired by some comments on the question "The history of the NULL pointer":-
There was a practice in the '70s to use the hexadecimal code 0xDEADBEEF to indicate an invalid value. This could be to fill memory that was freed after a previous…
Chenmunka
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34
votes
1 answer
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 Impedance meaning "absent on the bus", but actual…
SF.
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34
votes
3 answers
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 as follows:
10 rem L
Some programmers…
Psychonaut
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34
votes
5 answers
How did early computers deal with calculations involving pounds, shillings, and pence?
In the era before UK currency was decimal, how were accounting calculations involving pounds, shillings, and pence typically handled?
Were the underlying computations typically performed in terms of decimal fractions of pounds, in binary or decimal…
Brian Borchers
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34
votes
2 answers
What are the three or four holes on the back of a 3.5inch floppy disk indicating and used for?
Why do 3.5 inch floppy disks have sometimes three and others four holes on the backside? What's the difference, what do this holes indicate and what are these used for?
Bob Ortiz
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34
votes
8 answers
What made some 8-bit BASIC interpreters especially slow?
Most 8-bit systems had a BASIC interpreter that ran at a rate roughly commensurate with the CPU type, speed, memory bandwidth and interrupt status. Some systems, however, had interpreters that ran at a fairly dismal speed: I'm particularly thinking…
scruss
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34
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8 answers
Why were relays prevalent in early 1940s computers when vacuum tubes were also available?
Many of of the computers built in the 1940s used relays for logic (see here and here):
Bell Labs Model I, 1940
Bletchley Park Bombe, 1940
Zuse Z2, 1940
Zuse Z3, 1941
Bell Labs Model II, 1943
Bell Labs Model III, 1944
Harvard Mark I, 1944
Bell Labs…
DrSheldon
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34
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3 answers
How was OS/2 supposed to be crashproof, and what was the exploit that proved it wasn't?
I seem to remember that IBM claimed one of its versions of OS/2 was crashproof. I believe they specifically said it was "crashproof" or some similar term to indicate that it would never crash.
But someone came up with an exploit that caused OS/2 to…
pacoverflow
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17 answers
Did computer games for Commodore 64 really take "25 minutes" to load "if everything went alright"?
In the Swedish-language song "Nostalgi" by Markoolio from 2003, some of the lyrics go:
My first computer had 64 kB
you surfed on the water, and that's that
The computer games were loaded in from tapes
it took 25 minutes if everything went…
Kommendåre 64
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34
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15 answers
When did compilers start generating optimized code that runs faster than an average programmer's assembly code?
It is highly unrecommended to write your own code in assembly now since, in most cases, gcc -O3 does magic. But in the ‘80s it was believed that compiled C code takes 4(?) times or more than a well-organized assembly equivalent. When and why does…
Schezuk
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34
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9 answers
What did code on punch cards do with the other six bits per column?
In the fifties and sixties, program source code was typically stored on punch cards, one card per line.
The most common card format was the IBM 80 column by 12 row. For source code, this was commonly used as one character position per column, the…
rwallace
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34
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6 answers
How can I construct a dial-up network in my home, purely for the kicks?
All the technology in my house is modern, but I want to build a dialup network that I can use to produce sounds from Bell 101/103 (if I can find the proper softmodem) to V.92bis. I honestly don't know where to start here, but I do have multiple…
jediKatana
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34
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1 answer
When and where did the $ convention for hexadecimal literals originate?
I found this question asking about the origin of 0x to denote hexadecimal to be interesting.
However, when I cut my teeth programming on 8-bit 65xx systems in the early 80's everything I saw used a $ to denote hexadecimal digits (assemblers,…
Geo...
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4 answers
Why was 'echo on' chosen as the default setting within batch scripts in MS-DOS?
In my experience, just about every single MS-DOS (and thus Windows cmd) batch file starts with the line @echo off, to silently switch off echoing of the commands in the batch file to the console. This seems unnecessarily noisy, and raises the title…
hBy2Py
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34
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4 answers
Why are the homing bumps on D and K on Apple keyboards?
Some Apple keyboards, such as the Apple //e, some early Macintosh models, and the venerable Apple Extended Keyboard have the homing bumps on the D and K keys instead of the standard F and J keys that almost everyone else uses. (e.g. IBM's venerable…
user
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