INDIVIDUAL EDITING COMMANDS
Move (forward one line) M
The Move command causes the file pointer to be moved from its current position to the start of the following line. Attaching a repetition number to a Move command provides a means of moving forward a fixed number of lines. For example, the command "M99" issued at the start of the file, causes the pointer to be moved to the start of the hundredth line in the file. The command fails if the file pointer is at the very end of the file, that is, beyond the last line of text. It is legitimate to Move from the last line in the file to the end-of-file position, but then further Moves will fail.
Move back (one line) M-
This command causes the file pointer to be moved from its current position to the start of the previous line. The command fails if the current line is the first line in the file, the pointer being moved nonetheless to the start of this line.
Cursor Down }
This command is similar to the Move command, except that the pointer is moved to the column position in the following line corresponding to its position in the current line. The command is typically the definition of a cursor control key. With this and the other cursor movement commands, the resulting line position may be beyond the end of the line (that is, to the right of the last printing character). This is often a temporary state en route to another position, and so the fact that the cursor is out in space does not of itself imply any extension of the line, but if any text is entered in this situation, the gap between the existing end of the line and the file pointer is first filled with spaces. The command fails when the file pointer is on (or beyond) the last line of the file.
Cursor Up {
This command is similar to the Move Back command, except that the pointer is moved to the column position in the previous line corresponding to its position in the current line. See the notes on Cursor Down (above) The command fails when the file pointer is on the first line of the file, and the pointer does not move.
Right-shift (one char) R
This command causes the file pointer to be moved right one character position. The command fails if the file pointer is at or beyond the end of the current line. Hence "R*" takes the pointer from anywhere within the line to the right hand end of the line.
Left-shift (one char) L
This command causes the file pointer to be moved left one character position. The command fails if the file pointer is at the start of the current line. Hence "L*" takes the pointer from any position to the start of the line.
Cursor Right >
This command is similar to the Right-shift command except that it permits the file pointer to be moved beyond the end of the line, that is, beyond the rightmost character on the line. See the notes on Cursor Down. The Cursor Right command fails if the file pointer is at or beyond the maximum line length defined by WIDTH.
Cursor Left <
The Cursor Left command is identical in effect to the left-shift command. It is provided for reasons of symmetry.
Find TEXT F
The Find command causes the Editor to search forward in the file for the first occurrence of the specified text string. The search starts at the current position of the file pointer, except that an occurrence just at the file pointer which has already been matched, either by Find or by Uncover or Verify, is ignored. For example, adding a repetition count to a Find command, as in "F/cat/3", will locate the third occurrence of the sequence "cat". The repetition does not have to be in the form of a count attached to the original command. For example, it is a common experience to discover, after a Find has been executed once, that the character sequence chosen in fact appears earlier in the file than the intended position. In this case the Find command can simply be repeated, by typing 1 as a repetition command, until the desired occurrence is reached.
By default the search continues to the end of the file. The scope of the search may, however, be limited to a particular number of lines counting from (and including) the current line, by specifying the number of lines between the command letter and the quoted text. For example, "F9/cat/" limits the scope of the search to the current line and the next eight. The command fails if there is no occurrence of the specified sequence of characters within the scope of the search. Where the scope is more than one line, the file pointer is moved to the start of the last line searched (end-of-file in the case of unlimited scope). Where the scope is one line, the file pointer is not moved.
Find back TEXT F-
The Find back command is similar in effect to Find except that the search proceeds backwards through the file. The number of lines to be searched may be specified between the minus and the text parameter; by default the search continues to the start of the file. The command fails if there is no occurrence of the specified text within the scope of the search, the file pointer ending up at the start of the last line searched.
Traverse TEXT T
The Traverse command causes the first occurrence of the specified text to be located and the pointer to be positioned at the right-hand end of the occurrence, rather than at the start as with Find. The search proceeds as for Find except that the default scope is confined to the current line and that an occurrence of text already matched is not ignored. The command fails if there is no occurrence of the text string within the scope of the search. Pointer movement in the case of failure is exactly as for Find.
Verify TEXT V
The Verify command neither moves the file pointer nor alters the content of the file. It succeeds if the sequence of characters immediately to the right of the file pointer matches the text specified; otherwise it fails. The Verify command only has a use in conjunction with programmed commands (see the section on this topic).
Delete TEXT D
The Delete command causes the first occurrence of the specified text to be located and then deleted, leaving the file pointer at the site of the deletion. The search proceeds as for Find, except that the default scope is confined to the current line, rather than the rest of the file, and an occurrence of text already matched is not ignored. The command fails if there is no occurrence of the specified text within the scope of the command. Pointer movement in cases of failure is exactly as for Find.
Insert TEXT I
This command has the effect of inserting the text specified to the left of the file pointer. The text parameter which follows the letter "I" may take any of the following forms: quoted text between delimiter characters a text macro letter ('X'-'Z' or 'x'-'z') the ditto character the exclamation-mark The last-mentioned case ("I!") provides a direct-entry capability for inserting a text string within a line. The text to be inserted is requested when the Insert command is executed, with the video cursor at the position of the file pointer. The normal way of terminating the text is with RETURN; if any other control key is used as a terminator, it causes the command sequence currently being executed to be abandoned and the control key to be treated as a new command. This applies also to the use of this form for the other insertion commands (Overwrite, Substitute, and Get).
For the direct-entry form, in most implementations, a certain amount of space is opened up at the position of the file pointer to permit the text to be typed in. Then when the terminating key is pressed, the line is closed up again. In some implementations, no space is opened up, and the line automatically accommodates each character as it is typed. For typing convenience, the Editor relaxes some of the syntactic rules for all the insertion commands (Insert, Overwrite, Substitute and Get), but not for the text matching commands. The closing delimiter in the case of quoted text may be omitted if the text string is the last thing in a command line and the exclamation-mark indicating the direct-entry case may be omitted provided that no ambiguity could arise (that is, provided the immediately following character is not one of the text macro letters). Specifying a repetition count with Insert is a convenient way of inserting multiple characters, typically spaces. Insert fails if adding the text would cause the part of the line to the left of the pointer to exceed the maximum line length (as defined by WIDTH).
Overwrite with TEXT O
The Overwrite command provides a means of replacing existing text on a one-for-one basis by new text. It differs from Insert in that one character is deleted from the file for each character added, except that if the end of the line is reached, it functions identically to insertion. The possible forms of text parameter are as for Insert. The exclamation-mark form ("O!" or just "O") again provides a direct-entry capability for a single piece of text. It is useful only in command mode, since data-entry mode provides that capability all the time. The failure condition is the same as for Insert.
Substitute TEXT S
The Substitute command causes the text matched by an earlier Find (or Uncover or Verify) to be deleted and the text specified as parameter following the "S" to be inserted. The operation of substitution involves two text strings, one to be removed, the other to be inserted. In ECCE the first of these is established by one command, typically a Find, and the second is specified as the parameter to Substitute. Thus, for example, "F/this/ S/these/" will alter the first occurrence of "this" to "these". One advantage of splitting the function between two commands is that they can be issued independently and the effect of the Find checked before giving the Substitute. Substitute fails if the last positioning action was not a Find, Uncover or Verify, or the effect of inserting the text would exceed the maximum line length permitted by the Editor.
Get TEXT (one line) G
The Get command causes the text specified to be inserted as a complete line above the current line. The file pointer is moved to the start of the current line if it is not already there, but this remains the current line. The Get command is the way in which complete lines are inserted in a file. The most frequently used form is "G!" (or "G"). In this case the text is not embedded in the command as a text string, but is requested when the Get is executed by the Editor. A repeated Get expects a fresh line each time; it does not cause the first line typed to be inserted again. Thus "G!5" (or "G5") causes five lines to be requested and inserted, in the order typed, above the current line. The Get command fails if the line typed in starts with a colon. The failure condition is an arbitrary convention, which may be used to cause a repeated Get to terminate. In particular, it permits the use of "G!*" (or "G*") to insert an indefinite number of lines (which it would be inconvenient to have to count).
Kill & Kill back K K-
The Kill command "K" causes the whole of the current line to be deleted. The file pointer is left positioned at the start of the following line. Kill does not simply erase all the characters on a line leaving it blank; it removes the line altogether. Kill followed by Get (eg "KG" or "K2G3") is a common command sequence when replacing a number of complete lines by other complete lines. The command fails if the file pointer is at the end of the file. The Kill back command "K-" causes the whole of the line before the current line to be deleted. The file pointer is moved to the start of the current line. The command fails if the current line is the first line in the file, the pointer being moved nonetheless to the start of this line.
Erase (one char) E E-
The Erase command "E" causes the character immediately to the right of the file pointer to be deleted The command fails if the file pointer is at or beyond the end of the current line. Hence "E*" erases all characters on the line to the right of the pointer. The Erase back command "E-" causes the character immediately to the left of the file pointer to be deleted. The command fails if the pointer is at the start of the line. Hence "E-*" erases all characters to the left of the pointer.
Case-change (char) C
If the character immediately to the right of the file pointer is a letter of the alphabet, the Case-change command alters it to the corresponding letter in the other case, so that upper is mapped to lower and lower to upper. Whether the character is a letter or not, the pointer is moved one position to the right. The command fails if the pointer is at or beyond the end of the current line. Hence "C*" changes the case of all letters to the right of the pointer on the current line.
Uncover TEXT U
The Uncover command causes the first (or next) occurrence of the specified text to be located and all the material between the position of the file pointer at the start of the command and the occurrence of the text to be deleted. The text itself is not deleted. The search proceeds as for Find, except that the default scope is confined to the current line. The Uncover command is applicable where it is most convenient to specify a deletion as 'up to' a particular character or sequence of characters. With an explicit scope, Uncover can delete part of the starting line, a number of complete lines, and an initial part of the line in which the string is located. The command fails if there is no occurrence of the text string within the scope of the search. In the case of the default scope (current line only), the pointer is not moved and the line is not changed. In the case of a multi-line search, failure results in deletion of all material between the initial position of the pointer and the start of the last line searched, which is where the pointer ends up. An unlimited search can be specified by means of "U*".
Break (line in two) B
This command causes the current line to be split in two at the position of the file pointer; the second part becomes the current line. Break creates two lines from one. One of its uses is to split lines which may have become undesirably long as a result of insertions. Break with the pointer at the start of a line creates a blank line above the current line. There is no natural failure condition for this command; implementations generally impose an upper limit on the number of times it may be repeated.
Join (two lines) J
This command causes the following line to be appended to the current line, that is, it creates one line from two. The command fails if the current line already exceeds the length defined as the maximum line width. In the case of failure the pointer is positioned at the end of the current line.
Insert/Get back I- G-
The commands "I-" and "G-" re-introduce material which has been deleted from the file, the insertion being made at the position at which they are executed, which may or may not be the position at which the material was deleted. The order of recovery is the reverse of the order of deletion, and, in tune with this, these commands leave the file pointer in front of, rather than after, the newly inserted material. The use of these commands at a different site from that at which the material was deleted is the basic technique in ECCE of moving blocks of text from one position to another.
The command "I-" restores a single deleted character from the last alteration site in the file. The last alteration site is the position in the file at which a sequence of contiguous insertions and deletions was last carried out. All the material deleted at this site is eligible for insertion. It fails if there are no remaining deleted characters from that site. For example, the command "I-0" brings in at any point all the text deleted at the last alteration site, and the sequence "ERI-" (Erase, Right, Insert back) reverses the order of a pair of characters. The command "G-" restores a complete deleted line. All complete lines deleted from the file at any time in the course of the edit are available for recovery, not just those removed at the last alteration site. It fails if there are no further deletions to be restored. For example, "KMG-" (Kill, Move, Get back) reverses the order of a pair of lines.
Overwrite back O-
The command "O-" is an 'undo' command which can both restore material just deleted and remove material just inserted. It operates at the last alteration site in the file, irrespective of the position of the file pointer at the time the "O-" is executed. The last alteration site is the position in the file at which a sequence of contiguous insertions and deletions was last carried out. All the material deleted at this site is eligible for re-insertion, and all the inserted material is eligible for removal. Each execution of the "O-" command removes a single inserted character or line break and/or restores a single deleted character or line break. It fails if neither of these operations is possible. Hence "O-*" removes the effect of all the alterations at the site.
Print P
The Print command is used solely to achieve feedback from the Editor. It causes the current line to be displayed, and, if repeated, causes a Move to the following line.
Next/previous unit N N-
The Next command "N" locates the next word or matching punctuation symbol in the file to the right of the file pointer. If the character currently to the right of the pointer is a letter or digit or a space, or the pointer is at the end of the line, the pointer is moved to the beginning of the next word, where a word is defined as a sequence of alphanumeric characters (letters or digits) not preceded by an alphanumeric character. If the character is a left bracket (round, square or curly), the pointer is moved to the corresponding right bracket, taking account of nested occurrences of bracket symbols. If the character is any other symbol, the pointer is moved to the next occurrence of that symbol. In all cases, the unit located is regarded as having been matched by a text search (so that Substitute is valid, for example). The command fails if there is no occurrence of the appropriate kind of unit before the end of the file.
The Next back command "N-" locates the previous unit in the file, a unit being defined as for Next (above), with the role of left and right brackets reversed. It fails if there is no unit of the appropriate kind before the beginning of the file.
Query Spelling Q
The Query command is used to invoke a check on the form of the text starting at the current position of the file pointer. The nature of the check currently implemented is a simple spelling error detection. This is done by comparing words with entries in a limited dictionary of written English. The command fails if the check fails. Repeated execution implies advancing to the next unit for checking. Hence the command "Q*" causes the check to be performed on successive words until one fails, or the end of the file is reached.
Move to line number n #n
This command causes the file pointer to be moved from its current position to the start of the line specified. Lines are numbered from 1 at the start of the file and the numbers relate to the current state of the file, not its state at the start of editing. If no line number is specified in the command, one is requested at the time the command is executed. The command is executed as a Move or Move back as appropriate, and fails as for Move if the line number is too big. Note that the parameter <n> is not a repetition count.
Increment number by n +n
The Increment command (plus-sign) is used to add the value specified by <n> to the first number to the right of the pointer on the current line. For this purpose, a number is any sequence of decimal digits, or a single letter. This command is most useful when it is required to adjust more than one number by a constant amount. The value 1 is understood if <n> is omitted. The form "+-" may be used to specify a negative increment. Letters are included to cover the case where they are used to 'number' paragraphs. The command fails if there is no number to the right of the pointer on the current line, or the increment specified would take the item out of range. Note that the parameter <n> is not a repetition count.
Adjust line length A
The Adjust command is provided to simplify the task of maintaining a reasonably uniform line length within running text. In brief, it has the effect of breaking over-length lines and extending under-length lines by bringing up words from succeeding lines. The line length applied is as defined by the parameter WIDTH, and the left margin as defined by MARGIN The detailed specification which follows is quite complicated. The main points to note are: a single Adjust will make the current line an acceptable length and leave the file pointer at the start of the (perhaps revised) following line; A* will (try to) produce adjusted lines up to the end of a paragraph, a paragraph being understood to terminate with a blank line (or end of file).
(a) If the end of the file has been reached, the command fails with no effect. (b) If the current line (to the right of any margin) is blank, it is not changed and the file pointer is moved to the start of the following line. (c) If the length of the current line exceeds the defined maximum line length, the line is broken at the rightmost space character to the right of the file pointer which leaves a line not exceeding the maximum length, and a new line is formed from the latter part of the original line, with an added margin of spaces if MARGIN is non-zero. The file pointer is left at the effective start of the new line. The command fails if there is no space character satisfying the condition specified. (d) If the length of the current line is not greater than the maximum length, 'words' from succeeding lines are appended to the current line until either doing so would exceed the maximum length or a line which is blank to the right of the margin (or end of file) is reached. The latter case is a failure condition, but in all cases the file pointer ends up at the start of the line following the adjusted line. For the purposes of Adjust, a word is defined to be any sequence of characters terminated by a space or end of line. Appending a word implies inserting a space plus the word at the end of the first line, and removing the word plus its terminating space from the second line (removing the whole line in the case that the word is the only word on the line).
At column position n @n
The purpose of the 'at' command is to enable text to be aligned to a particular column position. The effect is that the part of the current line to the right of the file pointer is aligned to the column position specified by <n>. This is achieved by the insertion or deletion of spaces to the left of the file pointer. In the event that aligning to the column position specified would cause the length of the line to exceed the defined maximum line length, <n> is reduced to prevent this. Columns are numbered from zero upwards, so that, for example, @40 has the natural interpretation of placing text half-way along an 80-column line. Spaces to the right of the file pointer are not affected by this command, and only space characters immediately to the left of the file pointer are removed in seeking to align leftwards. Using "@" with a large <n> has the effect of right-aligning the text following the pointer. The @n command fails if space-deletion fails to achieve correct alignment. Note that the number <n> is not a repetition count.
Set Marker ^
Execution of the Set Marker command (caret or circumflex by itself) causes the current position of the file pointer to be noted for future reference The marker set by this command may be utilised, and cancelled, by any of the following commands: the Define Macro command the Revert to Marker command the Switch Inputs command A marker is also cancelled if the text surrounding it is deleted from the file.
Define Macro 'X'...'z' ^n
The Define Macro command (caret with accompanying number) serves to define one of the six text macro letters ('X','Y','Z','x','y','z') as selected by <n> (1 to 6 respectively). For example "^2" is used to define 'Y' and "^6" to define 'z'. The effect is to define the letter selected to stand for the sequence of text between the set marker and the current position, or, if no marker is set, the text just matched by a text matching command. Any existing definition of the letter is lost, and the marker is cancelled. Although text parameters typed within commands cannot, for syntactic reasons, contain line breaks, there is no such restriction on the definition of macro letters by means of this command, subject to an overall limit on length imposed by the implementation. However, multi-line text strings are valid only for the insertion group of commands, not for the text matching group. It is immaterial whether the marker is ahead of the current position or vice versa.
The command fails if no marker is set and the file pointer is not at a matched text position. For convenience, with a marker set, a second Set Marker command (that is, simple caret without accompanying <n>) is interpreted as Define Macro defining 'X'.
Revert to Marker =
The Revert command (equals-sign) has the property of restoring the file pointer to the position established by the last executed Set Marker. The marker is cancelled. The command fails if there is no marker set.
Toggle Destruction mode |
Successive execution of this command (vertical bar) alternately enters or leaves a special mode of operation called Destructive mode. In this state, any of the movement commands may be used in a destructive sense, that is in such a way as to delete all the material from the starting position to the position after executing the move. Existence of the state is indicated by a special prompt. Note that actual alteration commands are disallowed in this mode. The mode is most useful in conjunction with some of the more specialised movement commands such as Next, Cursor Down and Query.
Switch Inputs $
This command is used to switch from the main file to the secondary input or back again. Having switched to secondary input, any of the location commands may be used to move about within that file, but alteration commands are not valid. The current position in the two files is independent and is preserved when a switch is made between the two. When this facility is used, a separate window is created out of the screen region used for file display, to show the current part of the secondary input file. Apart from providing the facility simply to inspect another file while editing, the main use of secondary input is to enable material from the second file to be incorporated in the first. One way of doing this is to Define text macros to represent pieces of text in the secondary file and use these as parameters for Insert after switching back to the main file.
To provide a more convenient way of handling the most common requirements, the convention is also adopted that if a set marker is outstanding when a switch is made from secondary input to the main file, the text from the position of the marker up to the current position within the secondary file is immediately inserted in the main file. For example, incorporating the whole of a secondary file in the main file can be achieved by moving to the appropriate point in the main file and then giving the commands (separately or as one command line): $ ^ M* $ that is, Switch to secondary input, Set Marker, Move to end of file, Switch back to main file. Any marker set in the main file is cancelled on switching to secondary input.