"Pause button" redirects here. For the media control, see Media controls. For other uses, see Pause.
The Break key (or the symbol ⎉) of a computer keyboard refers to breaking a telegraph circuit and originated with 19th century practice. In modern usage, the key has no well-defined purpose, but while this is the case, it can be used by software for miscellaneous tasks, such as to switch between multiple login sessions, to terminate a program, or to interrupt a modem connection.
Break/Pause key on PC keyboard
Because the break function is usually combined with the pause function on one key since the introduction of the IBM Model M 101-key keyboard in 1985, the Break key is also called the Pause key. It can be used to pause some computer games.
A standard telegraph circuit connects all the keys, sounders and batteries in a single series loop. Thus the sounders actuate only when both keys are down (closed, also known as "marking" — after the ink marks made on paper tape by early printing telegraphs). So the receiving operator has to hold their key down or close a built-in shorting switch in order to let the other operator send. As a consequence, the receiving operator could interrupt the sending operator by opening their key, breaking the circuit and forcing it into a "spacing" condition. Both sounders stop responding to the sender's keying, alerting the sender. (A physical break in the telegraph line would have the same effect.)
The teleprinter operated in a very similar fashion except that the sending station kept the loop closed (logic 1, or "marking") even during short pauses between characters. Holding down a special "break" key opened the loop, forcing it into a continuous logic 0, or "spacing", condition. When this occurred, the teleprinter mechanisms continually actuated without printing anything, as the all-0s character is the non-printing NUL in both Baudot and ASCII. The resulting noise got the sending operator's attention.
This practice carried over to teleprinter use on time-sharing computers. A continuous spacing (logical 0) condition violates the rule that every valid character has to end with one or more logic 1 (marking) "stop" bits. The computer (specifically the UART) recognized this as a special "break" condition and generated an interrupt that typically stopped a running program or forced the operating system to prompt for a login. Although asynchronous serial telegraphy is now rare, the Break key once used with terminal emulators can still be used by software for similar purposes.
Sinclair
On the ZX80 and ZX81 computers, the Break is accessed by pressing Space. On the ZX Spectrum it is accessed by Caps Shift+Space. The Spectrum+ and later computers have a dedicated Break key. It does not trigger an interrupt but will halt any running BASIC program, or terminate the loading or saving of data to cassette tape. An interrupted BASIC program can usually be resumed with the CONTINUE command. The Sinclair QL computer, without a Break key, maps the function to Ctrl+Space.
BBC Micro
On a BBC Micro computer, the Break key generates a hardware reset which would normally cause a warm restart of the computer. A cold restart is triggered by pressing Ctrl+Break. If a filing system is installed, ⇧ Shift+Break will cause the computer to search for and load or run a file called !Boot on the filing system's default device (e.g. floppy disk 0, network user BOOT). The latter two behaviours were inherited by the successor to Acorn MOS, RISC OS. These behaviours could be changed or exchanged in software, and were often used in rudimentary anti-piracy techniques.
Because of the BBC Micro's near universal usage in British schools, later versions of the machine incorporated a physical lock on the Break key to stop children from intentionally resetting the computer.
Modern keyboards
On many modern PCs, Pause interrupts screen output by BIOS until another key is pressed. This is effective during boot in text mode and in a DOS box in Windows safe mode with 50 lines. On early keyboards without a Pause key (before the introduction of 101/102-key keyboards) the Pause function was assigned to Ctrl+NumLock, and the Break function to Ctrl+ScrLock; these key-combinations still work with most programs, even on modern PCs with modern keyboards. Pressing the dedicated Pause key on 101/102-key keyboards sends the same scancodes as pressing Ctrl, then NumLock, then releasing them in the reverse order would do; additionally, an E1hex prefix is sent, which enables 101/102-key-aware software to discern the two situations, while older software usually just ignores the prefix. The Pause key is different from all other keys in that it sends no scancodes at all on release in PS/2 modes 1 or 2, so it is impossible to determine whether this key is being held down with older devices. In PS/2 mode 3 or USB HID mode, there is a release scancode, so it is possible to determine whether this key is being held down on modern computers.[1]
On modern keyboards, the Break key is usually labeled Pause with Break below, sometimes separated by a line: Pause/Break, or Pause on the top of the keycap and Break on the front, or only Pause without Break at all. In most Windows environments, the key combination ⊞ Win+Pause brings up the system properties.
Keyboards without Break key
Compact and notebook keyboards often do not have a dedicated Pause/Break key.
Substitutes for Break:
Ctrl+Fn+F11 or Fn+B or Fn+Ctrl+B on certain Lenovo laptops.[2][3][4]
For some Dell laptops, without a Break key, press the Alt+Space and select "Interrupt".[8][6]
Usage for breaking the program's execution
While both Ctrl+Break and Ctrl+C combination are commonly implemented as a way of breaking the execution of a console application, they are also used for similar effect in integrated development environments.[9][10] Although these two are often considered interchangeable,[11] compilers and execution environments usually assign different signals to these.[12] Additionally, in some kernels (e.g. miscellaneous DOS variants) Ctrl+C is detected only at the time OS tries reading from a keyboard buffer and only if it's the only key sequence in the buffer,[13][14] while Ctrl+Break is often translated instantly (e.g. by INT 1Bh under DOS). Because of this, Ctrl+Break is usually a more effective choice under these operating systems; sensitivity for these two combinations can be enhanced by the BREAK=ONCONFIG.SYS statement.
^"Keyboard 101- and 102-Key". PS/2 Hardware Interface Technical Reference(PDF). IBM. October 1990. p. 19. Archived (PDF) from the original on 2022-10-09. Except for the Pause key, all keys are make/break.
^"Keyboard shortcut for Break, Pause, ScrLK, SysRq function on ThinkPad 6 rows Precision keyboard - ThinkPad - Lenovo Support US".
break, pause, button, redirects, here, media, control, media, controls, other, uses, pause, symbol, computer, keyboard, refers, breaking, telegraph, circuit, originated, with, 19th, century, practice, modern, usage, well, defined, purpose, while, this, case, u. Pause button redirects here For the media control see Media controls For other uses see Pause The Break key or the symbol of a computer keyboard refers to breaking a telegraph circuit and originated with 19th century practice In modern usage the key has no well defined purpose but while this is the case it can be used by software for miscellaneous tasks such as to switch between multiple login sessions to terminate a program or to interrupt a modem connection Break Pause key on PC keyboard Because the break function is usually combined with the pause function on one key since the introduction of the IBM Model M 101 key keyboard in 1985 the Break key is also called the Pause key It can be used to pause some computer games Contents 1 History 2 Sinclair 3 BBC Micro 4 Modern keyboards 5 Keyboards without Break key 6 Usage for breaking the program s execution 7 See also 8 References 9 External linksHistory EditA standard telegraph circuit connects all the keys sounders and batteries in a single series loop Thus the sounders actuate only when both keys are down closed also known as marking after the ink marks made on paper tape by early printing telegraphs So the receiving operator has to hold their key down or close a built in shorting switch in order to let the other operator send As a consequence the receiving operator could interrupt the sending operator by opening their key breaking the circuit and forcing it into a spacing condition Both sounders stop responding to the sender s keying alerting the sender A physical break in the telegraph line would have the same effect The teleprinter operated in a very similar fashion except that the sending station kept the loop closed logic 1 or marking even during short pauses between characters Holding down a special break key opened the loop forcing it into a continuous logic 0 or spacing condition When this occurred the teleprinter mechanisms continually actuated without printing anything as the all 0s character is the non printing NUL in both Baudot and ASCII The resulting noise got the sending operator s attention This practice carried over to teleprinter use on time sharing computers A continuous spacing logical 0 condition violates the rule that every valid character has to end with one or more logic 1 marking stop bits The computer specifically the UART recognized this as a special break condition and generated an interrupt that typically stopped a running program or forced the operating system to prompt for a login Although asynchronous serial telegraphy is now rare the Break key once used with terminal emulators can still be used by software for similar purposes Sinclair EditOn the ZX80 and ZX81 computers the Break is accessed by pressing Space On the ZX Spectrum it is accessed by Caps Shift Space The Spectrum and later computers have a dedicated Break key It does not trigger an interrupt but will halt any running BASIC program or terminate the loading or saving of data to cassette tape An interrupted BASIC program can usually be resumed with the CONTINUE command The Sinclair QL computer without a Break key maps the function to Ctrl Space BBC Micro EditOn a BBC Micro computer the Break key generates a hardware reset which would normally cause a warm restart of the computer A cold restart is triggered by pressing Ctrl Break If a filing system is installed Shift Break will cause the computer to search for and load or run a file called Boot on the filing system s default device e g floppy disk 0 network user BOOT The latter two behaviours were inherited by the successor to Acorn MOS RISC OS These behaviours could be changed or exchanged in software and were often used in rudimentary anti piracy techniques Because of the BBC Micro s near universal usage in British schools later versions of the machine incorporated a physical lock on the Break key to stop children from intentionally resetting the computer Modern keyboards EditOn many modern PCs Pause interrupts screen output by BIOS until another key is pressed This is effective during boot in text mode and in a DOS box in Windows safe mode with 50 lines On early keyboards without a Pause key before the introduction of 101 102 key keyboards the Pause function was assigned to Ctrl NumLock and the Break function to Ctrl ScrLock these key combinations still work with most programs even on modern PCs with modern keyboards Pressing the dedicated Pause key on 101 102 key keyboards sends the same scancodes as pressing Ctrl then NumLock then releasing them in the reverse order would do additionally an E1hex prefix is sent which enables 101 102 key aware software to discern the two situations while older software usually just ignores the prefix The Pause key is different from all other keys in that it sends no scancodes at all on release in PS 2 modes 1 or 2 so it is impossible to determine whether this key is being held down with older devices In PS 2 mode 3 or USB HID mode there is a release scancode so it is possible to determine whether this key is being held down on modern computers 1 On modern keyboards the Break key is usually labeled Pause with Break below sometimes separated by a line Pause Break or Pause on the top of the keycap and Break on the front or only Pause without Break at all In most Windows environments the key combination Win Pause brings up the system properties Keyboards without Break key EditCompact and notebook keyboards often do not have a dedicated Pause Break key Substitutes for Break Ctrl Fn F11 or Fn B or Fn Ctrl B on certain Lenovo laptops 2 3 4 Ctrl Fn B or Fn B on certain Dell laptops 5 6 Ctrl Fn S on some other Dell laptops 7 6 Fn Esc on Samsung Ctrl Fn Shift on certain HP laptops Fn R on certain HP laptops Fn Ctrl B on certain Logitech LOGI keyboards Substitutes for Pause Fn P or Fn Ctrl P or Fn Alt P on certain Lenovo laptops 4 Fn B on certain Dell laptops 4 6 Fn Shift on certain HP laptops Fn W on certain HP laptops For some Dell laptops without a Break key press the Alt Space and select Interrupt 8 6 Usage for breaking the program s execution EditWhile both Ctrl Break and Ctrl C combination are commonly implemented as a way of breaking the execution of a console application they are also used for similar effect in integrated development environments 9 10 Although these two are often considered interchangeable 11 compilers and execution environments usually assign different signals to these 12 Additionally in some kernels e g miscellaneous DOS variants Ctrl C is detected only at the time OS tries reading from a keyboard buffer and only if it s the only key sequence in the buffer 13 14 while Ctrl Break is often translated instantly e g by INT 1Bh under DOS Because of this Ctrl Break is usually a more effective choice under these operating systems sensitivity for these two combinations can be enhanced by the a href BREAK CONFIG SYS directive html class mw redirect title BREAK CONFIG SYS directive BREAK a ON CONFIG SYS statement See also EditSystem request Scroll lock Num lockReferences Edit Keyboard 101 and 102 Key PS 2 Hardware Interface Technical Reference PDF IBM October 1990 p 19 Archived PDF from the original on 2022 10 09 Except for the Pause key all keys are make break Keyboard shortcut for Break Pause ScrLK SysRq function on ThinkPad 6 rows Precision keyboard ThinkPad Lenovo Support US Ctrl Break key Thinkpads Forum a b c T530 Pause Break key Thinkpads Forum Dell Inspiron 17 specification PDF Archived PDF from the original on 2022 10 09 a b c d Break Pause Key No Longer Available on Some Dell XPS Latitude and Precision Laptops Dell US www dell com Retrieved 2023 05 05 Dell community DELL Commonly Used Keystroke Shortcuts Dell com Retrieved 18 February 2018 CTRL C Break Msdn microsoft com 2010 03 30 Retrieved 2010 10 22 Debug Break Msdn microsoft com 2010 03 30 Retrieved 2010 10 22 Ctrl Break definition of Ctrl Break in the Free Online Encyclopedia Encyclopedia2 thefreedictionary com Retrieved 2010 10 22 www gnu org https web archive org web 20121022172337 https www gnu org software emacs windows ntemacs discuss subproc ctrl c Archived from the original on October 22 2012 a href Template Cite web html title Template Cite web cite web a Missing or empty title help Vim documentation vim online Vim org Retrieved 2010 10 22 ClipX DOS 5 0 Ref int 23h ctrl c handler Ousob com Archived from the original on 2016 03 04 Retrieved 2010 10 22 External links Edit Media related to Break key at Wikimedia CommonsIBM PC keyboard Windows ANSI US layout vteEsc F1 F2 F3 F4 F5 F6 F7 F8 F9 F10 F11 F12 PrtScn SysRq ScrollLock Pause Break Insert Home PgUp NumLock Delete End PgDn 7 8 9 4 5 6 1 2 3 Enter 0 Ins Del Retrieved from https en wikipedia org w index php title Break key amp oldid 1153314597, wikipedia, wiki, book, books, library,
