Hot answers tagged

124 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, ...
user avatar
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 ...
user avatar
  • 96.5k
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 ...
user avatar
  • 5,647
57 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 ...
user avatar
  • 173k
34 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 ...
user avatar
  • 2,924
27 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 ...
user avatar
  • 1,388
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 ...
user avatar
  • 21.9k
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 ...
user avatar
  • 32.5k
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, ...
user avatar
22 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 ...
user avatar
  • 173k
20 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, ...
user avatar
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'...
user avatar
  • 57.3k
19 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 ...
user avatar
  • 17.2k
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 ...
user avatar
  • 96.5k
19 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 ...
user avatar
  • 173k
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 ...
user avatar
  • 271
16 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 either The physical end of a medium, The end of the used portion of a medium The end ...
user avatar
  • 173k
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 ...
user avatar
  • 7,609
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....
user avatar
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) ...
user avatar
  • 7,664
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 ...
user avatar
  • 7,609
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 (...
user avatar
  • 173k
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 ...
user avatar
  • 4,510
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 ...
user avatar
  • 1,779
9 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 ...
user avatar
  • 28k
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 ...
user avatar
  • 181
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 ...
user avatar
  • 3,872
8 votes
Accepted

When did tabs start defaulting to 8 columns?

I believe the only way we can answer this question is by members finding 'the earliest' such description. DEC's first CRT terminal device, the DEC VT05 terminal (1970), had tab stops fixed at 8-...
user avatar
  • 28.3k
7 votes

What characters which were in use at the time were excluded from ASCII?

Small letters. These were included in the 1967 ASCII standard but not the 1963 one.
user avatar
  • 2,058
7 votes

What file systems / encapsulation formats used ASCII control characters?

The codes in question were normally used to simulate special interrupts and/or control cards. The idea is that you could take a stack of 80-column punch cards (for instance) and translate them as a ...
user avatar

Only top scored, non community-wiki answers of a minimum length are eligible