61 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 ...
Raffzahn's user avatar
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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, ...
manassehkatz-Moving 2 Codidact's user avatar
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 ...
scruss's user avatar
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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 ...
Raffzahn's user avatar
  • 219k
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 ...
Chenmunka's user avatar
  • 8,111
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-...
Paul_Pedant's user avatar
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 ...
Maury Markowitz's user avatar
5 votes

Did any system ever use the Privacy Message (PM) C1 control?

GNU Screen recognizes PM ... ST and uses it to display a short popup message to the user. (Basically ignoring the "Privacy" part of the name.) Like with other sequences, it seems to only ...
grawity's user avatar
  • 455
5 votes

How did control characters work in real teletypes?

Teletypes were self contained units simply executing the code received. For most codes that simply meant printing a certain character and advance by one position. Others advanced paper by one line (...
Raffzahn's user avatar
  • 219k
3 votes
Accepted

How did control characters work in real teletypes?

For actual Teletypes, which are electromechanical devices whose output is ink on paper, there were these ways to move the print position (there was no actual cursor): Carriage return: mechanically ...
dave's user avatar
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2 votes

What file systems / encapsulation formats used ASCII control characters?

Data transmission and text file handling are not truly separate aspects in many operating systems. This is very evident in DOS and unix systems, where special files that map to character ...
rackandboneman's user avatar
2 votes

Did any system ever use the Privacy Message (PM) C1 control?

[Caveat: This is distilled from the only application I've ever seen using the PM/ST mechanic] But, what is a "privacy discipline"? Stuff specific to an application. My guess is that it ...
Raffzahn's user avatar
  • 219k
1 vote

How did control characters work in real teletypes?

Real teletypes were pure electromechanical devices with no CPU, or any electronic components at all. On receiving a line feed code the paper was advanced a line or with a carriage return the printing ...
LMiller7's user avatar
  • 111
1 vote

History of Ctrl-S and Ctrl-Q for flow control

As a user of teletypes and serial communications back in the 1970s - this is my understanding as well. There were hardware signals for "flow control". Was thinking you set bits on UART which then ...
user14983's user avatar

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