\chapter{Glossary Of Obscure TECO Terms} \label{Glossary Of Obscure TECO Terms} \begin{description} \item[Accent grave] The \escape character. Echoed for TECO's text and command string delimiter when an ESCape surrogate is in effect. Actually set as the ESCape surrogate by the 8192 ET bit. \item[Abort-on-error bit] The 128's bit of the ET flag. If this bit is set, then TECO will abort execution on encountering an error (after printing the error message) and control returns to the operating system. This bit is initially set when TECO starts up, but is reset whenever TECO issues its prompt. \item[{\tt }] One of several characters that TECO treats specially for use as a delimiter. Known as ESCAPE in more recent times, but traditional TECO users will still go on ending their command strings with {\tt }. \item[Anchored search] A search ({\tt S}) or search and replace ({\tt FS}) command that is preceded by a {\tt ::}. This indicates that the search must match the characters immediately following the current pointer position. If these characters do not match, no further searching is performed and the text buffer pointer does not move. \item [Argument pair] A command of the form {\tt m,n} where {\tt m} and {\tt n} are numbers (or TECO commands that return numbers). When used before a command that normally acts on lines, the argument pair causes the command to work on characters. The characters specified by this argument pair is the set of characters between pointer positions {\tt m} and {\tt n}. The number {\tt m} should normally be less than or equal to {\tt n}. \item[ASCII code ] The American Standard Code for Information Interchange. The code used by TECO to represent characters internally. Consult Appendix A for details. \item[{\tt @}-sign modified command] A command that is preceded by an {\tt @}-sign modifier. \item[{\tt @}-sign modifier] An at-sign ({\tt @}) that proceeds a command. It indicates to TECO that the string argument to the command is to delimited on both sides by a user-supplied delimiter rather than to be delimited only at the end by a TECO-designated delimiter (normally {\tt }). \item[Automatic refresh] A refresh of the buffer display done when scrolling is active (when {\tt 7:W} is non-zero) just before TECO issues its asterisk prompt. Automatic refresh can be disabled by the 128 ED bit. \item[Automatic type out] The feature of TECO that causes lines of text to be automatically typed out. The ES flag may be used to control the automatic type out of lines after search commands, and the EV flag may be used to cause automatic type out of lines after command execution. \item[Auto-trace mode] A mode that TECO goes into when the 4's bit of the EH (Help-level) flag is set. In this mode, TECO will automatically print out the erroneous command string after an error occurs. \item[Backup protection] The process of preserving the user's original file (as a backup) when editing that file with the {\tt EB} (Edit with Backup) command. \item[Backwards searches] A search that proceeds in the backwards direction. If the string being looked for does not occur at the current pointer position, the pointer position is moved back one character and the search is tried again. This continues until the string is found or until the boundary of the search has been reached or until the beginning of the current text buffer has been reached. Backward searches are initiated by using a negative argument to a search command or by using an argument pair {\tt m,n} with {\tt m} greater than {\tt n} to an {\tt FB} or {\tt FC} command. \item[Bounded searches] A search command that requires searching only a portion of the text buffer. Of particular importance is the case where you only want to search the current line for a given string. Bounded searches are accomplished using the {\tt FB} command. \item[Case flagging] A mode of TECO wherein, on type out, it will flag alphabetic characters (in either upper or lower case) by preceding them with a single quote. Lower case flagging is particularly useful on terminals that do not display lower case. Case flagging is controlled by EU, the case flag. Setting EU to 0 sets lower case flagging mode; setting EU to 1 sets upper case flagging mode, and setting EU to -1 removes all case flagging. \item[Character-oriented editor] An editor that allows modification of single characters, so that if just one character of a line is wrong, the entire line does not have to be retyped. TECO is a character-oriented editor (although it has a number of facilities for dealing with text lines, too). \item[Colon-modified command] A command that is preceded by a colon ({\tt :}) modifier. \item[Colon-modifier] A colon preceding a TECO command, used to indicate that the action of the command is to change. Frequently indicates that the command is to return a value (-1 if the command succeeded, 0 if the command failed). \item[Command line ] The current line of the command string that is being typed into TECO. \item[Command string scope editing] The feature of TECO that is enabled when editing is performed on a CRT terminal. In this mode, typing the immediate action {\tt } command causes the character deleted from the command string to physically disappear from the screen. Other commands, such as {\tt } also behave differently, taking best advantage of the properties of a video terminal. \item[Command string] The string of TECO commands that is currently being typed into TECO, or is currently being executed by TECO. \item[Comment ] An informative message used within a TECO program, to make the code more readable. The comment explains the meaning and purpose of the associated TECO commands. The comment is enclosed in exclamation marks. \item[Compile-class command] A set of operating systems commands (such as {\tt COMPILE}) that causes compilation (translation) of a source file written in a computer language into machine instructions. The {\tt EG}\escape command is useful to finish an editing session and re-execute the last compile-class command (normally a command that compiles the file that was just edited). \item[Conditional ] A TECO language construct used to specify code to be conditionally executed depending upon the results of some test. The most general form of the TECO conditional is \begin{verbatim} n"X | ' \end{verbatim} which tests the number n using condition X (See section \ref{Branching Commands} for details). The commands specified by the {\tt } are executed if the condition succeeds, otherwise the commands specified by the {\tt } are executed. \item[Control-character] An ASCII character whose octal code is in the range 0-37. Usually denoted in this manual by {\tt } where {\tt X} is the character whose ASCII code is 100 (octal) greater than the ASCII code for the control character being represented. TECO displays such a character as \caret {\tt X} (Caret-X) except for {\tt }, {\tt }, {\tt }, {\tt }, and {\tt } which have their normal display, and {\tt } which is displayed as \$ (dollar sign) or, if a user-designated ESCAPE surrogate is in effect, as \escape (accent grave). Anytime a single control-character, {\tt } is a valid TECO command, the two-character sequence, \caret {\tt X}, may be used instead. \item[{\tt } trapping] A mode of operation wherein a TECO macro will regain control (rather than TECO) when {\tt } or {\tt } is typed on the user's terminal to abort execution of the current command string. {\tt } trapping is enabled by setting the high-order bit of the ET flag. \item[Current character] The character immediately following the current text buffer pointer position. \item[Cursor] A visible pattern on a CRT terminal (usually blinking) that would specify to a true scope editor (like VTEDIT) the current location of the text buffer pointer, or which would specify the location where subsequently typed characters would be displayed. \item[{\tt }] Terminology in this manual for an ESCape typed at the console and passed to TECO. On newer terminals, there may be no \fbox{ESCAPE} key. Some versions of TECO provide for an ``ESCape surrogate'', a user-designated key which is to cause transmission of an ESCape to TECO. The term {\tt } is used to indicate an ESCape transmitted to TECO whether it was generated by the designated ``surrogate'' key or by a ``real'' \fbox{ESCAPE} key. An ESCape types out as \escape when a surrogate is active, but as {\tt \$} when no surrogate is active. \item[Destructive search] A form of global search in which pages of text that are passed over (because they did not contain the string being searched for) are discarded rather than written to the output file. Destructive searches are initiated in TECO via use of the {\tt \_} command. \item[Display editor] A true display editor is on which makes efficent use of a CRT terminal or display scope. Such an editor maintains a {\em window} into the text being edited. As characters are typed on the terminal, these characters immediately are entered into the text buffer and the window is immediately updated to reflect this change. With the help of some macro support, TECO can be made to be a true display editor. A more modest use of a CRT terminal (and which requires no macro support) is scrolling, q.v. \item[Dot ] A mnemonic for {\em the current text buffer pointer position}. Stems from the fact that the . (dot, or period) TECO command returns this number as its value. \item[{\tt E} command ] One of several two-character TECO commands that start with the letter {\tt E}. \item[Echo mode ] A normal mode of operation in which TECO will automatically echo (display) each character that is typed in response to a \caret {\tt T} command. Opposite of no-echo mode. This mode is controlled by the 8's bit of the ET flag. (0 means no-echo mode.) \item[ED flag ] The edit level flag. \item[Edit-class command] A type of operating system command (such as MAKE and TECO) that specifies that file editing is to occur. Many operating systems remember the argument specified with the last Edit-class command, so that the next time an edit-class command is used without an argument, the previous argument can be recalled. \item[Edit level flag] A bit-encoded flag, referenced by the {\tt ED} command, that describes how TECO should behave with reference to certain features. See section \ref{Mode Control Flags} for more details. \item[Edit verify flag] A flag that describes how TECO should act after processing of a command string. This flag can be set so that TECO will display the line just edited on the terminal after each command. See section \ref{Mode Control Flags} for more details. \item[EH flag ] The help level flag. \item[Either-case search mode] A standard mode of operation in which alphabetic characters specified within a search string are permitted to match a corresponding character of either upper or lower case. \item[Else-clause ] The part of a conditional command that is executed if the condition is not satisfied. In TECO, these are the commands that occur between the | and the ' characters within the conditional construct. \item[End-of-file flag] A read-only flag, referenced by the \caret {\tt N} command that specifies whether or not end-of-file has been seen on the currently selected input stream. A value of 0 means that end-of-file has not been seen; a value of -1 means that end-of-file has been reached. This flag is initially 0 and is reset to 0 each time a new file is selected for input. \item[EO level ] The current version level of TECO-10. \item[ES flag ] The search verification flag. \item[{\tt } ] The character whose ASCII code is 33 (octal). It is a general-purpose delimiter used by TECO. Traditionally known as an {\tt }. When no ESCape surrogate is active, an ESCape types out as \$ (dollar sign). See also {\tt }. \item[ESCape surrogate] A character (designated via the 8192 ET bit, or via the EE flag) which causes an ESCape to be transmitted to TECO. When an ESCape surrogate is active, an ESCape types out as \escape (accent grave). See also {\tt }. \item[ET flag ] The terminal characteristics flag \item[EU flag ] The upper/lower case flag. \item[EV flag ] The edit verify flag. \item[Exact-case search mode] A mode of operation in which alphabetic characters within a search string must match the exact case (upper case or lower case) of characters specified. \item[Exit Protection] A protective feature of TECO that prevents a user from exiting TECO if a potential los of data is imminent. The {\tt EX} and {\tt EG} commands ` are aborted (with the {\tt ?NFO} error message) if there is text in the text buffer, but no output file is open. \item[F command ] One of several two-character TECO commands that start with the letter 'F'. \item[Flag ] A data register used by TECO to control various modes of operation. The contents of the flag are set by specifying the new value before the flag name; and the contents are returned by using the flag name without a numeric argument. The TECO flags are: \caret X, \caret E, \caret N, ED, EE, EH, EO, ES, ET, EU, and EV. \item[Flow command ] A TECO-11 command that is used to flow (branch) to a particular flow control character. The flow commands are {\tt F<}, {\tt F>}, {\tt F'}, and {\tt F|}. \item[Form feed flag] A read-only flag, referenced by the \caret {\tt E} command that specifies whether the previous append from the input file terminated because of encountering a form feed character in the input file, or because the text buffer became nearly full. The value of this flag is automatically set to -1 by TECO if input is terminated by the presence of a form feed character in the input file. \item[Garbage collection] A process used by TECO-10 to collect unused memory when more memory is required. \item[Global Q-register] A Q-register available throughout all macro levels (including ``outside'', or at prompt level). Global Q-registers are named A-Z and 0-9. See also \ref{Local Q-Registers}, and section \ref{Q-registers}. \item[Global search ] A type of search that continues through the entire input file until the specified characters are found. Successive pages of the file are read into the text buffer and then written out into the output file (if the string is not located). Global searches in TECO are initiated via the {\tt N} command. \item[Hard-copy editing mode] A mode of operation that TECO uses when the user's terminal is not a CRT. In this mode, when a character is rubbed out using the {\tt } key, the rubbed-out character is re-typed on the terminal as a visible indication that this character was rubbed out. Opposite of scope editing mode. This mode can be entered, even on a scope terminal, by turning off the 2's bit of the ET flag. \item[Help level flag] A bit-encoded flag, referenced by the {\tt EH} command, that controls properties of TECO having to do with error messages and user assistance. \item[Immediate command] A special command to TECO that takes immediate effect, requiring no {\tt }s to begin its execution. {\em Immediate action editing characters} are commands such as {\tt} and {\tt}, which perform editing of the TECO command string currently being typed in. See section \ref{Immediate Action Editing Characters}. An {\em immediate inspection command} is a single-character command which can be typed as the very first character after TECO's prompting asterisk, and which causes the current location counter to be moved by one line and the new current line to be typed out. Examples are {\tt } and {\tt }. See section \ref{Immediate Inspection Commands}. {\em Immediate action commands} are other commands] which may be typed right after TECO's prompting asterisk, such as the *q to save the previously-typed command in a Q-register or the \caret W to re-display a scrolling buffer window. See section \ref{Immediate Action Commands}. {\em Immediate ESCape sequence} commands are invoked by keys which generate escape sequences, such as arrow or ``auxiliary keypad'' keys. See section \ref{Immediate ESCAPE-Sequence Commands}. Such commands are usually used to perform editing of the TECO command string currently being entered into TECO. For example, the commands {\tt} and {\tt} are immediate action commands. \item[Iteration ] A language construct that permits a sequence of operations to be re-executed indefinitely or a given number of times. In TECO, this is accomplished by enclosing the commands in angle brackets. \item[Kernel ] The TECO-11 kernel refers to the TECO-11 module that implements all those features of TECO-11 that are common to all PDP-11 operating systems. Operating system specific features and the interface to the operating system is accomplished by linking an I/O module tailored for the desired operating system with the kernel. \item[Keypad editor ] A true scope editor that uses special keys on the terminal (such as a VT52 or VT100) to control editing functions. VTEDIT is an example of a keypad editor. \item[Line ] A portion of text delimited by {\tt }, {\tt }, {\tt }, or the beginning or end of the text buffer. The final delimiter is considered to be part of the line. \item[Line-numbered file] In TOPS-10, an ASCII file that contains line numbers embedded in the start of each line. TECO does not require these line numbers, but can handle them if they are present. They can also be generated or suppressed via the {\tt /GENLSN} and {\tt /SUPLSN} switches respectively. \item[Line-oriented editor] An editor that primarily uses line numbers to direct editing, and most of whose commands are line-oriented. TECO is a character-oriented editor, but also has many facilities that work with lines. \item[Line-wrap mode] A standard mode of TECO's window support wherein lines that are too long to fit on a single physical line of the user's terminal are automatically continued on the next line. Opposite of truncate mode. \item[Literal type out mode] A mode that TECO can be put into by setting the 1's bit in the ET flag, or (for a single character on a one-shot basis) by using the :\caret {\tt T} command. In this mode, any characters typed by a TECO program via use of one of the commands {\tt T}, {\tt V}, \caret {\tt A}, or {\tt :G}, will be displayed on the user's terminal without any modification. When not in this mode, TECO will convert characters that normally do not print to a form that can be displayed on the user's terminal (e.g. {\tt } displays as \caret {\tt X} and {\tt } displays as \$ or, if a user-designated ESCAPE surrogate is in effect, as \escape). Literal type out mode is useful when trying to do real-time displays on a CRT terminal. Normal (up-arrow) mode is particularly useful to let you see what characters are really in your file. \item[Local Q-register] A Q-register available to only a single macro level (including ``outside'', or at prompt level). The local Q-registers for a particular macro level are automatically saved and restored by TECO around execution of a lower-level macro. Local Q-registers are named .A-.Z and .0-.9. See also \ref{Global Q-Registers}, and section \ref{Q-registers}. \item[Log file ] An audit trail that TECO-10 can keep showing all the commands that were typed to TECO and/or all the type out made by TECO. This is useful for reviewing what went wrong with a ``bad'' edit. The log file is initiated with the {\tt EL} command (see Appendix \ref{Incompatible, Obsolete and System-Specific Commands}. \item[Macro ] A sequence of TECO commands intended to be loaded into a Q-register and executed as a TECO program. \item[Macro level ] Two commands within the same TECO macro are said to be at the same macro level. When one TECO macro calls another, the calling macro is said to be at the higher macro level, and the called macro at the lower macro level. \item[Match control construct] A command, consisting of certain special characters, used within a search string to indicate to TECO that special groups of characters are permitted to match at this point. \item[Memory expansion] TECO's act of acquiring additional storage from the operating system when the currently allocated storage is insufficient to handle the current TECO command. Typically, TECO will attempt to acquire this additional memory before it completely runs out of memory, so as to allow a {\em buffer zone} for the user. This allows him to complete a few more commands even in the case where TECO is unable to get more memory. The informative message {\tt [nK Bytes]} or its equivalent is printed on the terminal informing the user that memory usage has expanded. \item[Mung ] A recursive acronym for {\em Mung Until No Good} an act applied by novice TECO users to their source files. \item[MUNG command ] An operating system command used to invoke a pre-written TECO program. The most general form of this command is {\tt MUNG file,data} where {\tt file} is the name of a TECO source program, and {\tt data} is data to be passed to that program. \item[No-echo mode ] A mode of operation in which TECO will not automatically echo (display) the character typed by the user in response to the \caret {\tt T} command. This mode is entered by setting the 8's bit of the ET flag. Opposite of echo mode. \item[Page ] A portion of text delimited by form feeds. The form feeds are not considered to be part of the page. Sometimes the term {\em page} is used to refer to all the text currently in the text buffer. \item[Panic Mode ] A condition that occurs (on small, single-user operating systems), when, in the middle of outputting during an edit, the output device fills up so that the I/O transfer cannot continue. TECO recovers gracefully from this condition by printing the {\tt ?FUL} error message and returning control to TECO without any loss of data. At this point, the user closes the current output file and opens another one on another device (with more room) and resumes editing. At a subsequent time, the two parts of his file can be concatenated back together. \item[Pipeline editor] An editor which only makes sequential edits to a file. The file to be edited is read into the text buffer one piece at a time. Each piece is edited and then written out. Once a piece has been written out, further editing to that piece is not possible unless the output file is re-opened in a later edit as a new file to be edited. TECOs are pipeline editors, with the exception of TECO-11 on VAX/VMS (which offers the capability to page backwards as well as forward). \item[Pointer preservation mode] A mode of operation in which the text buffer pointer will not change after a failing search. This mode is controlled by the 16's bit of the ED flag. \item[Primary input stream] A term used by TECO-11 to refer to the main input file that TECO is using. \item[Primary output stream] A term used by TECO-11 to refer to the main output file that TECO is using. \item[Prompt level ] A TECO command is said to be executed from prompt level if it was typed in directly in response to TECO's prompt, as opposed to being executed from a macro. \item[Q-register ] One of 36 global or 36 local user-accessible registers provided by TECO. Each Q-register can hold both a number and a string of text. Of particular importance is the ability to store TECO command strings in Q-registers to be used as {\em macros}. \item[Q-register push down list] A last-in first-out stack available to users for saving and restoring the contents of Q-registers. \item[Read-with-no-wait mode] A mode of operation in which the \caret {\tt T} command will not hang until a key is typed on the user's terminal. In this mode, if no key has been struck, TECO returns a -1 as the value of the \caret {\tt T} command. This mode is entered by setting the 32's bit of the ET flag. \item[Scope editing mode] A mode of TECO in which command line scope editing (q.v.) algorithms are used. This mode is enabled by setting the 2's bit of the ET flag. It is usually automatically enabled by TECO if the operating system can detect that the user has invoked TECO from a scope terminal. Opposite of hard-copy editing mode. \item[Scrolling ] A form of TECO operation available on CRT terminals capable of supporting split-screen operation. The bottom n lines are used for TECO's asterisk prompt and the usual typed command lines; the remaining lines above are used for an automatically-updated window into the text buffer. A valuable training aid: one can experiment with TECO commands and immediately observe their effects. Not a bad idea for advanced users, either. Controlled by the {\tt n,7:W} command. \item[SEALL mode ] A mode of window operation in which all characters have a distinctive visible display, including characters such as {\tt }, {\tt }, and {\tt }, which normally do not print. Controlled by the 3:W flag (see section \ref{Scope Commands}). Also known as {\em View all} mode. \item[Search verification flag] A flag, referenced by the {\tt ES} command, that controls the action of TECO subsequent to the execution of a command string containg a search command. Proper setting of this flag will enable the user to verify that the search located the correct string, by having the line containing the string found displayed on the terminal. See section \ref{Mode Control Flags} for more details. \item[Search mode flag] A flag, referenced by the \caret {\tt X} command, that controls how TECO treats alphabetical characters within search strings. This flag is used to put TECO into either exact-case mode, or either-case mode. If the \caret X flag is set to 0, then either case matches in searches. If the \caret X flag is set to 1, then exact case matches are required. \item[Secondary input stream] A term used by TECO-11 to refer to an auxiliary input {\em channel} that was formed by use of the {\tt EP} command. \item[Secondary output stream] A term used by TECO-11 to refer to an auxiliary output channel that was formed by use of the {\tt EA} command. See section \ref{Secondary Stream Commands} for details. \item[Split Q-registers] The feature of TECO that permits storing of both a number and a string within a Q-register. Each Q-register can be considered to consist of two compartments. \item[String build construct] A command, consisting of special characters, used within a text argument to build up the contents of the text argument from other components. \item[SUPER TECO mode] A mode of TECO-8 wherein TECO will read past the end-of-file mark {\tt } of a sequential ASCII file. This mode is enabled by using the {\tt /S} switch on an {\tt ER} or {\tt EB} command and is terminated when an {\tt ER} or {\tt EB} command is issued with no {\tt /S} switch. This mode is useful for scanning through mass storage devices in an attempt to recover data from files that had previously been deleted. \item[Switch] A construct of the form {\tt /SWITCH} used within a command that takes a filespecification, to modify the action of the command or attributes of the file specified. Also known as a qualifier. \item[Tag ] A label specified within exclamation marks to mark a point within a TECO program. Control can be transferred to this point by the use of a GOTO ({\tt Otag}\escape) command. \item[TECO ] Text Editor and COrrector program. \item[TECO.INI ] A file containing TECO commands that is used as a user's private initialization file. When TECO starts up, it looks for such a file in the user's area, and if it finds one, the TECO commands in this file are executed before editing commences. \item[TECO.TEC ] A TECO macro used by many operating systems to parse the user's edit-class commands. \item[TECO I/O mode ] A mode of I/O operation under the RSTS/E and RSX-11 operating systems, in which the system buffers most characters and returns control to the caller (usually TECO) only when interesting characters (such as {\tt}, {\tt }, etc.) are typed. \item[TECO's prompt ] refers to the asterisk ({\tt *}) that TECO prints to indicate that it is ready to accept commands. \item[TECO SIG ] A DECUS Special Interest Group, consisting of users who are dedicated to the spread of, improvement of, and standardization of TECO. \item[Terminal characteristics flag] A bit-encoded flag, referenced via the ET command, that contains information about the user's console terminal and specifies in what manner TECO should support it. \item[Text buffer] The main buffer used by TECO to hold the text to be edited. \item[Text buffer pointer] A pointer that marks the position within the text buffer where TECO currently is. This pointer always points to positions between characters; it never points at a character. The current character is considred to be the character immediately to the right of the current position of the text buffer pointer. \item[Then-clause ] The set of commands within a conditional that are executed if the condition is satisfied. In TECO, these commands immediately follow the {\tt "X} at the start of the conditional. They are terminated by a {\tt |} or {\tt '} character. \item[Tracing ] The act of watching the command-by-command execution of a TECO program. This is accomplished by putting TECO into trace mode, via use of the ? command. \item[Trace mode ] A mode of TECO wherein each command that is executed by TECO is also displayed on the user's terminal as it is being executed. This mode is useful for debugging complicated TECO programs. TECO is toggled in and out of this mode via use of the ? command. See section \ref{Tracing} for more details. \item[Truncate mode ] A mode of TECO's window support wherein lines that are too long to fit on a single physical line of the user's terminal are truncated when the right margin of the scope is encountered. This mode is entered by setting the 256's bit in the ET flag. Opposite of line-wrap mode. \item[Type-out-time command] A special command that makes sense only while TECO is typing out text on the terminal. These commands are {\tt }, {\tt }, and {\tt } and affect the type out. \item[Up-arrow mode ] A standard mode of operation wherein upon type out, TECO will display control characters by typing the visible two-character sequence \caret {\tt X} to represent the control character {\tt }. On many older terminals, the caret character (\caret ), whose octal ASCII code is 136, prints as an up-arrow. Some control characters are not printed in up-arrow mode, notably {\tt }, {\tt }, {\tt }, {\tt }, and {\tt }. \item[Upper/lower case flag] A flag, referenced by the {\tt EU} command, that specifies whether or not case flagging is to occur. If set to -1, no case flagging occurs. If set to 0, lower case characters are flagged on type out. If set to +1, upper case characters are flagged on type out. \item[View all mode ] A mode of window operation in which all characters have a distinctive visible display, including characters such as {\tt }, {\tt}, and {\tt }, which normally do not print. Controlled by the {\tt 3:W} flag (see section \ref{Scope Commands}). Also known as SEALL mode. \item[War and Peace mode] A mode of operation in which TECO outputs a large informative paragraph of information automatically upon encountering an error in a user's program. This paragraph of information describes the error in painstaking detail and tells the user how to recover. This mode is entered by setting the help level to 3. This mode is particularly useful to Novices and particularly obnoxious to experts. \item[Window ] The portion of the text buffer that is currently being displayed on the user's terminal or auxiliary display device. \item[Window support] Assembly language code, built into TECO, that maintains a window into the text buffer on the user's terminal or auxiliary display device. \item[Yank protection] A feature of TECO wherein any {\tt Y}, {\tt\_}, or {\tt F\_} command that will potentially destroy valid data is aborted. This mode is normally enabled and will cause any of the aforementioned commands to abort with the {\tt ?YCA} error message if there is text in the text buffer and an output file is open. This feature can be disabled by turning off the 2's bit in the ED flag.