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Diffstat (limited to 'static/unix-v10/man4/dc.4')
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diff --git a/static/unix-v10/man4/dc.4 b/static/unix-v10/man4/dc.4 new file mode 100644 index 00000000..b161f0eb --- /dev/null +++ b/static/unix-v10/man4/dc.4 @@ -0,0 +1,214 @@ +.pa 1 +.he 'DC (IV)'6/12/72'DC (IV)' +.tr | +.ti 0 +NAME dc -- DC-11 communications interfaces +.sp +.ti 0 +DESCRIPTION +.br +.in 8 +The special files +/dev/tty0, /dev/tty1, ... +refer to the +DC11 asynchronous communications interfaces. +At the moment there are ten of them, but the number is subject +to change. + +When one of these files is opened, it causes +the process to wait until a connection is established. +(In practice, however, user's programs seldom open these +files; they are opened by init____ and become a user's standard +input and output file.) +The very first typewriter file open in a process becomes +the control_______ type____writer______ +for that process. The control typewriter plays a special +role in handling quit or interrupt signals, as discussed +below. +The control typewriter is inherited by a child process during a fork____. + +A terminal associated with one of these files ordinarily +operates in full-duplex mode. Characters may be typed at any time, +even while output is occurring, and are only lost when the +system's character input buffers become completely +choked, which is rare, +or when the user has accumulated the maximum allowed number of +input characters which have not yet been read by some program. +Currently this limit is 150 characters. +When this is happening the character "#" is echoed for every lost +input character. + +When first opened, +the interface mode is +ASCII characters; +150 baud; +even parity only accepted; +10 bits/character (one stop bit); +and newline action character. +The system delays transmission after sending certain function characters. +Delays for horizontal tab, newline, and form feed are calculated for +the Teletype Model 37; +the delay for carriage return is calculated for the GE TermiNet|300. +Most of these operating states can be changed +by using the system call stty(II). +In particular +the following hardware states are program settable independently +for input and output (see DC11 manual): +134.5, 150, 300, or 1200 baud; +one or two stop bits on output; +and 5, 6, 7, or 8 data bits/character. +In addition, the following software modes can be invoked: +acceptance of even parity, odd parity, or both; +a raw mode in which all characters may be read one at a time; +a carriage return (CR) mode in which +CR is mapped into newline on input and +either CR or line feed (LF) cause echoing of +the sequence LF-CR; +mapping of upper case letters into lower case; +suppression of echoing; +suppression of delays after function characters; +the printing of tabs as spaces; +and setting the system to handle IBM|2741s. +See getty(VII) for the way that terminal speed and type are +detected. + +Normally, typewriter input is processed in units of lines. +This means that a program attempting +to read will be suspended until an entire line has been +typed. Also, no matter how many characters are requested +in the read call, at most one line will be returned. +It is not however necessary to read a whole line at +once; any number of characters may be +requested in a read, even one, without losing information. + +During input, erase and kill processing is normally +done. +The character "#" erases the +last character typed, except that it will not erase +beyond the beginning of a line or an EOT. +The character "@" kills the entire +line up to the point where it was typed, but not beyond an EOT. Both these +characters operate on a keystroke basis independently +of any backspacing or tabbing that may have been done. +Either "@" or "#" may be entered literally by preceding +it by "\\"; +the erase or kill character remains, but the +"\\" disappears. + +It is possible to use raw mode in which +the program +reading is awakened on each character. +In raw mode, no erase or kill processing is done; +and the EOT, quit and interrupt characters +are not treated specially. + +The ASCII EOT character may be used to generate an end of file +from a typewriter. +When an EOT is received, all the characters +waiting to be read are immediately passed to +the program, without waiting for a new-line. +Thus if there are no characters waiting, which +is to say the EOT occurred at the beginning of a line, +zero characters will be passed back, and this is +the standard end-of-file signal. +The EOT is not passed on except in raw mode. + +When the carrier signal from the dataset drops (usually +because the user has hung up his terminal) any read +returns with an end-of-file indication. +Thus programs which read a typewriter and test for +end-of-file on their input +can terminate appropriately when +hung up on. + +Two characters have a special meaning when typed. +The ASCII DEL character (sometimes called "rubout") +is the interrupt_________ signal. +When this character is received from a given typewriter, +a search is made for all processes which have this typewriter +as their control typewriter, +and which have not informed the system that they wish +to ignore interrupts. +If there is more than one such process, one of these is +selected, for practical purposes at random. +The process is either forced to exit +or a trap is simulated to an agreed-upon location +in the process. +See intr(II). + +The ASCII character FS is the quit____ signal. +Its treatment is identical to the interrupt signal +except that unless the receiving process has +made other arrangements it will not only be terminated +but a core image file will be generated. +See quit(II). +The character is not passed on except in raw mode. + +Output is prosaic compared to input. +When one or more +characters are written, they are actually transmitted +to the terminal as soon as previously-written characters +have finished typing. +Input characters are echoed by putting them in the output queue +as they arrive. +When a process produces characters more rapidly than they can be typed, +it will be suspended when its output queue exceeds some limit. +When the queue has drained down to some threshold +the program is resumed. +Even-parity is always generated on output. +The EOT character is not transmitted to prevent terminals +which respond to it from being hung up. +.sp +The system will handle IBM|2741 terminals. +See getty(VII) for the way that 2741s are detected. +In 2741 mode, +the hardware state +is: +134.5 baud; +one output stop bit; +and 7 bits/character. +Because the 2741 is inherently half-duplex, +input is not echoed. +Proper function delays are provided. +For 2741s without a feature known as "transmit interrupt" +it is not possible to collect input ahead of the time that +a program reads the typewriter, +because once the keyboard has been enabled there is no way +to send further output to the 2741. +It is currently +assumed that the feature is absent; +thus the keyboard is unlocked only when some program reads. +The interrupt signal (normally ASCII DEL) is simulated +when the 2741 "attention" key is pushed to generate either +a 2741 style EOT or a break. +It is not possible to generate anything corresponding to +the end-of-file EOT or the quit signal. +Currently IBM EBCDIC is default for input and output; +correspondence code output is settable (see stty(I)). +.tr || +The full ASCII character set is not available: +"[", "]", "{", "}", "~", are missing on input and are printed as blank on output; +"c|" is used for "\\"; +"_" for "^"; +" " for both "'" and"`"on output; +and " " maps into "'" on input. +.tr | +Similar mappings occur with correspondence code output. +.sp +.in 16 +.ti 0 +FILES /dev/tty[01234567ab] 113B dataphones +.br +/dev/ttyc display data set +.br +/dev/ttyd 113B with /dev/dn1 +.sp +.ti 0 +SEE ALSO kl(IV), getty(VII) +.sp +.ti 0 +BUGS The +primarily Model 37 oriented delays +may not be appropriate +for all other ASCII terminals. +.tr || |