125
votes
Accepted
Why wasn't ASCII designed with a contiguous alphanumeric character order?
Why is ASCII this way?
First of all, there is no one best sorting order for everything. For example, should UPPER or lower case be first? Should numbers be before or after letters? Too many choices, ...
68
votes
Accepted
Why are the symbols on the number keys of PC & Mac keyboards different to ASCII keyboards?
It all dates back to typewriters, but the two layouts aren’t ASCII v. non-ASCII, they’re mechanical v. electric.
The !" etc. layout was common on mechanical typewriters, based on the layout used for ...
- 118k
62
votes
Why wasn't ASCII designed with a contiguous alphanumeric character order?
According to ASA X3.4-1963 Appendix A, one of the design considerations was:
(7) Ease in the identification of classes of characters
Furthermore:
A4.4 The character set was structured to enable ...
- 6,849
60
votes
Accepted
History of Ctrl-S and Ctrl-Q for flow control
Which OS was the first to use Ctrl-S and Ctrl-Q on the console for pause and continue?
TL;DR;
It's been developed independently of anything one might call an OS (*1). It's (nowadays) called Software ...
- 213k
35
votes
Why wasn't ASCII designed with a contiguous alphanumeric character order?
man 7 ascii of Linux Programmer's Manual says,
Uppercase and lowercase characters differ by just one bit and the ASCII character 2 differs from the double quote by just one bit, too. That made it ...
- 3,084
28
votes
Accepted
Why wasn't EBCDIC designed with contiguous alphanumeric characters?
There is a clue in the name - BCD stands for "binary-coded decimal", where 4 bits are used to represent 1 decimal digit (0-9). The hexadecimal values A-F are not used in BCD.
EBCDIC is an extended ...
- 1,626
25
votes
Executable ASCII files before x86?
If you go back a lot before the x86, this technique wasn't unusual at all. In fact, writing programs using printable letters and symbols was pretty much the norm for early computers, except that there ...
- 26.1k
25
votes
Accepted
How does the shift key in a keyboard work?
That's how the shift key sometimes worked on old terminals and ASCII is designed around it.
But on a modern keyboard, the SHIFT key just does exactly the same as every other key on the keyboard: it ...
- 36k
24
votes
History of Ctrl-S and Ctrl-Q for flow control
First OS is hard to say. The codes go back to the 1960s with the Teletype Model 33. I have a hunch the original usage was not part of an operating system but at a lower level. In later times, ...
24
votes
Accepted
C64/PETSCII block graphic symbol: was there ever a logical reason for their "ASCII" codes?
The "PETSCII" encoding is based on keyboard positions of the original PET chicklet keyboard (*1):
(Taken from Wikipedia)
The keyboard is made similar to basic typewriter keyboards, but ...
- 213k
22
votes
What was the ASCII end of medium (EM) character intended to be used for?
Wikipedia
“Intended as means of indicating on paper or magnetic tapes that the end of the usable portion of the tape had been reached.”, if en.wikipedia.org/wiki/C0_and_C1_control_codes#EM is to be ...
- 20.5k
21
votes
Why wasn't EBCDIC designed with contiguous alphanumeric characters?
As pointed out by Jon Custer, part of the reason is due to the input at the time being punch cards. If holes were close together there was a risk of the card being unreadable or ripping.
In addition, ...
- 663
21
votes
Accepted
What was the ASCII end of medium (EM) character intended to be used for?
TL;DR;
EM (or EOM as in early documents - and Unicode as well) was and is widely used in data transmission to mark
the physical end of a medium,
the end of the used portion of a medium, or
the end of ...
- 213k
20
votes
Accepted
When did IBM start to use ASCII?
TL;DR:
ASCII was never intended for processing, just as an interface standard for data exchange (hence the name American Standard Code for Information Interchange)
IBM never switched, it still uses ...
- 213k
20
votes
Accepted
Why was PETSCII based on an obsolete version of ASCII?
TL;DR PETSCII isn't "based on ASCII". Rather, the specifications Commodore wanted for PETSCII caused them to "back into" supporting the only version of the ASCII standard that didn'...
- 60.1k
19
votes
When did IBM start to use ASCII?
IBM started using ASCII before 1970; the 2260 terminal, released in 1964, used the unpublished (but ratified) 1965 version of the ASA X3.4 standard.
IBM mainframes still use EBCDIC, so I don’t think ...
- 118k
17
votes
Why wasn't ASCII designed with a contiguous alphanumeric character order?
This chart (showing the hexadecimal values of ASCII characters) outlines manassehkatz's answer graphically:
Numbers are at 0x30 + the value of the number
Capital letters are at 0x40 + the value of ...
- 271
15
votes
History of Ctrl-S and Ctrl-Q for flow control
It was nothing to do with an OS as such. Ctrl-S and Ctrl-Q are simply XON and XOFF in ASCII.
These codes are used in serial communications to pause and resume sending.
With hardware handshake on ...
- 8,031
15
votes
Accepted
What's the deal with System/360's "USASCII" mode?
I found the explanation in chapters 23 and 20 of Mackenzie, Charles E, Coded Character Sets, History and Development (Addison-Wesley, 1980), which was linked in a footnote to Wikipedia's ASCII article....
14
votes
Why are the symbols on the number keys of PC & Mac keyboards different to ASCII keyboards?
It all dates back to the age of typewriters.
Using an ASCII-based layout made the design of computer keyboard encoders simpler, as the output of any key while holding Shift (capitals, symbols) ...
- 8,036
12
votes
Executable ASCII files before x86?
It was standard practice on the Sinclair ZX80 & ZX81 to put executable code into a REM statement at the beginning of a BASIC program.
REM statements are, of course, text comments, so this meets ...
- 8,031
11
votes
Executable ASCII files before x86?
Short Answer
It can be done in any environment that:
Allows the remarking of data files into program files,
Has a loader format that's either primitive enough or all readable
Has a character set (...
- 213k
10
votes
C64/PETSCII block graphic symbol: was there ever a logical reason for their "ASCII" codes?
I think the codes were laid out so that when laid out sensibly on the PET keyboard, the shifted and unshifted forms of each key would have a consistent relationship. When the VIC-20 reduced the ...
- 34.7k
10
votes
Accepted
Why ASCII paper tape has lower bit punched from the narrow side?
If you want to read it as octal, having the low order 3 bits grouped together is handy. Many of the early ASCII tables showed the codes in octal. HEX makes more sense once your computers begin to ...
- 6,128
9
votes
Executable ASCII files before x86?
I remember doing this on the university mainframe around 1975. This was on an ICL1904S. Note that the 1900 series had been around for more than 10 years at that time. I don't know when the feature ...
- 2,447
9
votes
Why do BK computers have unusual representations of $ and ^
The solution is rather simple, as the BK is using KOI8 with Graphic symbols in row Ax/Bx. KOI8 is somewhat similar to ISO 8859, as the lower 128 symbols are equivalent to ISO 646-IRV (*1,2,3,4). ISO-...
- 213k
8
votes
Executable ASCII files before x86?
For a slightly interesting twist on this concept, consider Control Data mainframes.
These beasts included not only a CPU, but a "peripheral processing unit" (PPU)1--and the CPU sent commands to the ...
- 4,742
8
votes
Why wasn't ASCII designed with a contiguous alphanumeric character order?
None of the existing answers consider the context of the development of ASCII. Remember, the first version of the standard was released in 1963.
At the time, hexadecimal notation was neither popular ...
- 15.8k
8
votes
Why wasn't ASCII designed with a contiguous alphanumeric character order?
Oldstyle ASR-33 teletype machines (telex machines) only handled 7-bit codes. They only handled uppercase English-language characters, the ten digits, and some punctuation.
They printed with this ...
- 181
8
votes
What was the ASCII end of medium (EM) character intended to be used for?
The EM marker goes back way before computers. As early as the 1850s, the telegraph system was making more efficient use of the wired network assets by offline punching of paper-tape, and store-and-...
- 461
Only top scored, non community-wiki answers of a minimum length are eligible