The C Users' Group Library 1994 August

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The e screen editor Page 1 eeeee ee ee ee ee eeeeeeeeeee ee ee eeeeeeeee TUTORIAL GUIDE AND IMPLEMENTATION MANUAL The e screen editor is full-screen editor designed for creating and modifying the source text of programs. It is not, and it is not intended to be, a word processor. It is released through the C Users Group for private non-profitmaking use by G. Nigel Gilbert MICROLOGY Version 4.8 October 1984 The e screen editor Page 2 Contents 1. Prerequisites 2. Introduction 3. Development history 4. Why e was written 5. How e works 6. Using e 7. Implementing e on your terminal 8. Changing the default settings of the options 9. Compiling and loading e 1. Prerequisites The editor is written in the programming language C and the source code is available in the public domain for non-profit use. It is recommended that you also have to hand a copy of the BDS C compiler, version 1.50 or later, if you need to reconfigure the editor to suit your terminal and your choice of default option settings. The editor can be configured simply to run under CP/M with any moderately sophisticated terminal. The following screen control functions must be available with the terminal: clear to end of line, clear to end of page, line insert, and line delete. It is probably not worth using or adapting e to run on terminals that do not support these functions (among the terminals which DO support these functions are: the TVI 910, 912, 920, 925, 950 series, Hazeltine 1420, 1500, Executive and Esprit series, ADM-31 (but not the ADM-3a), DEC VT52 and VT100, ADDS range, Visual 50 and 55 and other terminals which offer emulations of these). Also required is CP/M, version 2, or CP/M 3.1 (CP/M Plus), and at least 48K (and preferably 56K) of RAM. Other versions of CP/M might well do. 2. Introduction This document has sections on: the 'philosophy' of e - why it was written to work the way it does (sections 3, 4 and 5) using e (section 6) implementing e (sections 7, 8, and 9) The e screen editor Page 3 3. Development history e was written over a period of about two years to satisfy my own need for a decent screen editor to use for programming, primarily in C, but also in FORTRAN and Pascal. During that time, it has developed and changed. I expect that it will continue to do so, and hope that other users will keep in contact with me about what they think of it, what changes they make to it and how it could be improved. I can be contacted at: G. Nigel Gilbert MICROLOGY 4 Deanery Road Godalming GU7 2PQ Surrey England 4. Why e was written The design of e was determined largely by my own specific needs. I already possessed a copy of WordStar, the well-known, massive and generally excellent word processing package. I also possessed a copy of the well- known and entirely excellent BDS C compiler. Unfortunately, the two do not mesh well together. In practice, programming in C (or in any other compiled language) requires one to edit a program file, run the file through the compiler, locate errors, then re-edit the file to make corrections, and repeat all this a large number of times. The faster the cycle can proceed, the faster is program development. However, because WordStar is a big and powerful package, with two overlays to read off disk into memory, it can take over 25 seconds from the moment the command line is typed to being able to edit the program text. Moreover, the C compiler, like many others, reports syntax errors by line number; WordStar has no command to move the cursor to a specified line number. All in all, WordStar is great for text, and not much good for programs. I resolved, therefore, to write an editor more adapted to my needs. Such an editor would have the following characteristics (in rough order of priority): Small run file, with no overlays No initial menu - one would go straight into editing the text A command to jump to a given line number Random access to the text; as far as possible, it should be as quick to move from line 500 to line 1 as from line 1 to line 500 As few 'modes' as possible - I don't like editors (such as, for instance the UCSD editor) where one can only insert in the 'insert' mode, and only delete in the 'delete' mode No (unreasonable) limit on the size of files which can be edited As crash proof as possible - including guards against BDOS errors and disk and directory full errors Auto-indent feature for structured programming languages Capability of listing selcted portions of programs to the printer, whilst remaining inside the editor The e screen editor Page 4 e does all of these. On the other hand, there are a number of facilities which other editors possess, but which e does not have. They are all features which, if implemented, would conflict with one or more of the above 'desirables'. An editors is the kind of the thing for which personal preferences are important and varied, and thus your favorite feature may be in the list below, rather than the list above. If so, you can always have a go implementing it. (If you do, I'd be glad to have a copy, and so probably would the User Group). Macros and multiple commands executed repeatedly (in my view, these are more appropriate to a batch, rather than an interactive editor; and, anyway, such commands are difficult to formulate so that they do exactly what is wanted and neither more nor less) Wild characters and regular expressions in defining search strings for the Find and Alter commands (possible to implement, but would reduce the searching speed significantly) An 'Overwrite' mode as well as an 'Insert' mode (see comments above about modes) Word processing capabilities, such as word wrap and re-formating (I use WordStar) Block moves of arbitrary blocks, rather than just blocks of complete lines (fine, but the coding is hair-raising) At one time or another, I've tried all these latter features, but eventually given up or thrown them out as unnecessary or unproductive. The e screen editor Page 5 5. How e works The above list of desirables more or less dictated the basic design principles of e. For instance, the need to get to a particular line suggested that the text being edited should be organised in lines (as opposed to a continuous block of text, including end-of-line markers). The former organisation is that adopted by e (and by EDIT-80); the latter by ED and WordStar. The choice has a profound impact on the style of the resulting editor. Since text lines are of variable length, it would not be sensible to store then in fixed length 'holes'. e therefore keeps a list, in line order, of pointers to the text itself, which is kept packed in no particular order in a large block of memory. Text moving commands therefore have only to manipulate the pointers, not the text itself. Deleting a line just means deleting a pointer, by shifting the following line pointers down one. Inserting a line requires adding the text to the block of memory and making room in the list of pointers for a new one, to point to the new text. In fact, things are rather more complicated because it is not possible to keep all the text of large files in memory. When e runs out of memory space, it switches to using 'virtual memory'. The block of real memory used to store text is divided logically into 1K byte 'pages'. When there is no more room, the least recently used page is written to a scratch file on disk, thus making available another 1K bytes. e keeps track of where each page is located - in memory or on disk - and if the text of a line on a page which is currently not in memory is required (to display or change, for instance), another page is swapped out to disk, and the required page is swapped in. This technique means that any line can be accessed either immediately (if its text is already in memory), or in the time needed to write out a 1K block and read in another. It might appear that the only file size limitation that this would impose would be the amount of disk space available, but in fact one needs to keep all the line pointers in RAM for the sake of reasonable speed of line insertion and deletion. Thus the limitation is not in the size of the file which can be edited, but in the number of lines (the limit is quite large - about 4000 lines in a 56K CP/M system). The e screen editor Page 6 6. Using e This section describes how one uses e. It assumes that you have it already implemented for your terminal. Guidance on how to do that is to be found in sections 7 to 9. This section is organised as a tutorial. It is best to carry out the operations on your own terminal as they are described. The notes in the left hand margin are provided for quick reference. Start up a) Login to a drive (say, drive B:) containing a disk holding (at least) the files e.com (the editor) and e.doc (this document), and type e b) This will start the editor. You should see a screen which is blank except for the message '1:1' near the middle of the Status line top line, and the cursor at the start of the second line. The top line is used by e as its 'Status Line', showing information about what it is doing. The '1:1' shows that the cursor is on line 1, at column 1. c) Type I am using the e screen editor You will see what you type appearing on the screen, and the cursor keeping ahead of the characters you type. d) Now hold down the control (CTRL) key, and type V (ie type ^V). The top few lines will be filled by the 'help menu', Help menu guidance on the commands e will accept. The line you typed, and the cursor, will have moved down to make room for the help menu. e) The keys you press to issue commands to e will generally be either control keys (ie the 'control' key in combination with one of the letter keys), or special keys particular to Key-command the terminal you are using. For instance, to move the cursor assignments to the end of the text using a TeleVideo terminal, one presses the key marked HOME. Other terminals may not have such a key, and would use a control key instead. The following tutorial uses the key assignments used with the TeleVideo terminal range, but remember that there may be differences for your terminal. The help menu will tell you which particular keys you should be using. f) Press the left arrow key. The cursor will move one position to the left, so that it is on top of the 'r' of left arrow 'editor' key g) Type ^S. The cursor will jump leftwards to the beginning left word of the previous word, 'screen'. Type ^D, and it will jump a word to the right, back to the 'e' of 'editor'. Now press the right arrow right arrow key several times to move the cursor along the word 'editor' to the end of the sentence. Note that when the cursor reaches the end, it will not move any further, even if you keep pressing the right arrow key. The e screen editor Page 7 beginning of h) Type ^B. The cursor jumps to the Beginning of the line. line ^E takes it to the End of the line. Try it. Type ^B again, end of line and then type Now followed by a space. See how the new word is inserted before what you had there. This editor is always in 'insert' mode - whatever you type (that isn't a command) goes into the text, pushing aside anything already there. i) Press the Return key. This puts the cursor, and whatever Return is under and following it on a new line. On terminals which support the feature, only the line on which the cursor is resting will be in 'bright' characters; the rest of the text will be dimmer. Type at this moment new line and then type ^N. Note how, like Return, ^N inserts a new line, but this time, the cursor has stayed where it was, and did not move down to the new line. j) Using the up arrow and down arrow keys, and the keys you up arrow have used before, 'steer' your way round the text, noting how down arrow you can't escape the invisible boundaries which surround it. end of text The HOME key will take you to the end of the text, and the ^U beginning key will take you to the beginning. of text Move to the end of the text, and type Return to bring you onto the next line. Now type a tab (ie press the key marked Tab, or if there isn't one, type ^I). The cursor will have jumped across to column 8. Type the word auto indent Auto Now press Return again. The cursor moves to the next line, but not at the beginning but under the A of Auto. Type a tab and then the word indent and press Return. This time, the cursor is positioned under the i of indent. This is the auto indent feature at work: whenever you type Return and the previous line begins with 'white space' (blanks or tabs), the cursor is left immediately under the first non-blank and non-tab character of that line. It is very useful when writing programs that are 'block- structured' (such as C and Pascal) as it helps line up the indentations of each block without you having to worry about counting tabs or spaces. If you need to 'un-indent', it is easy to delete the unwanted spaces and tabs (we'll see how in a moment). The e screen editor Page 8 k) Move to the beginning of the text and type ^F. A prompt find under the menu will ask Find? Type ito and press Return. A second prompt will ask Search Backwards/Ignore case/number of time? Just press Return. The cursor will jump to the characters find options 'ito', in the middle of the word 'editor', and the prompts will disappear. You have found 'ito'. Now move the cursor to the end of the text (HOME), and press ^F again. After the prompt has appeared, type ^R. The previous characters to find ('ito') will be Retrieved. Press Return, to get the Search Backwards/Ignore case/number of times? prompt. This time, type 'b' (or 'B', or '^B', it doesn't matter) to mean that the search is to go backwards, and then press Return. The cursor will once again be positioned on the 'ito' of 'editor'. l) Type ^R. e will repeat the last Find command, attempting to find another 'ito', again working backwards. However, repeat since there is no other 'ito' in the text, the search will last find/ fail, and a message to say that appears on the status line. alter The cursor remains where it is. This is what happens whenever you ask e to search for something it cannot find. m) Now type ^A. This is the command to Alter (change, exchange) one set of charactacters (string) for another. The alter familiar Find? prompt will appear. Type the letter e. You will be asking e to change all the 'e's in the text to 'z's. Press Return, to get another prompt: Alter to? Type z, and press Return. Then comes the third prompt: Back/Global/To end (start)/Ignore case/Without asking/number? alter options You can now enter one or more of the initial letters - B G T I or W - of these options, and/or a number. The options mean: Back search backwards, towards the beginning of the file from the current cursor position Global replace all occurences of the specified string wherever they are in the text The e screen editor Page 9 To end replace all occurences of the specified string from the cursor start position to the end of the file (or the beginning if the Back option is also chosen) Ignore search for the find string without regard to the case, upper or case lower, of the characters Without replace without first verifying that the replacement is desired asking number find the next (number) occurences of the string To change all the 'e's in the text to 'z's, type g and Return. e will find the first 'e', place the cursor over it, and then ask, on the status line, whether a replacement of this 'e' is required. Type Y (or y or ^y) to effect the replacement. The cursor will move on to the next 'e'. Type N to skip replacing this one. Then the next ... please yourself Escape whether you change this one. And the next... press the Escape key (ESC) key this time, and the Alter command will be aborted, without making this change. This is the first use you have made of the Escape key, which plays an important role with e. The Escape key will almost always either abort the current command or skip some part of it. Another example of the useful Escape key: Move the cursor to the beginning of the file (^U). Type ^F, and ask to find 'ito'. Of course, you have done this before. But instead of pressing the Return key (and getting the Search Backwards/Ignore case/number prompt), press Escape. The cursor skips straight to the desired string in the word 'editor', using the default options: search forwards, once. n) Your text is probably getting to be a bit of a mess. delete left Let's delete it. Press the DEL key (RUBOUT on some keyboards). The character to the left of the cursor gets delete right erased. Now type ^G. The character under the cursor disappears. Move the cursor to the beginning of the file delete word again (^U), and type ^T. The word to the right of the cursor (it should be Now, if you've followed all these instructions exactly) is rubbed out. Try ^T again - nothing happens. ^T will not erase newlines. ^Y will, though. ^Y will erase the delete line whole of the line containing the cursor, and put the cursor on the first character of the next line. Move the cursor onto the line containing the word 'using' and type ^Y. It will disappear. Move the cursor to the end of the text (HOME), and press delete space Return. The auto indent will leave the cursor in column 16 on provided by the next line. Press DEL (RUBOUT) once, and note how the Tab auto indent provided by the auto indent is deleted, moving the cursor back to column 8. Press DEL again, and the cursor is back at the left hand margin, in column 1. Sometimes you might erase a word (or make other changes) by undo accident, or as an experiment to see how things look. e has an 'undo' key which will put the text back into the exactly the state it was in before the last change. In fact, e The e screen editor Page 10 remembers the last 40 text changing commands you have made, and pressing the 'undo' key repeatedly will undo each of them in turn. Position the cursor at the beginning of the word 'this' and type ^T. 'this' will disappear. Now press the 'undo' key (^\). 'this' reappears. Keep pressing the 'undo' key, and watch the changes you made being undone. When all is undone, the message, 'Nothing to undo' will appear. o) Type ^Q, to get the prompt quit Write edited text to file, Abandon all edits, or Return? R, for Return, will get you back into editing, and W, for Write, will ask for a name to file the text under. But you will probably not want to save your work this time, so type A quit options (or a or ^A). This results in: Exit to CP/M, Return to this file, or edit Another file? E, for exit, will put you back into CP/M. R is the panic button to return you to the text you were editing, in case you decided you didn't really mean that you wanted to abandon all that you had done. A, for another file, is the one we'll choose this time. Type A. (Incidentally, suppose you had wanted to file your text and exit to CP/M - the most common sequence. You would type Q W E, to quit, write and exit, a quick and easy set of commands, since Q W and E are the top left keys on a QWERTY keyboard) p) The screen will change to a display of the directory of the currently logged in directory. See that the amount of room you have left on the disk is displayed at the bottom changing righthand corner of the screen. To look at another directory, drive or type the drive letter, followed by a colon and Return. For user area instance, try typing A: followed by pressing Return. This now becomes the 'default' drive for reading and writing files. You can also can the user area you are logged into by typing the user area number followed by a / and Return. Now get back to the original directory, and type E.DOC as the file to edit. We shall be trying out some editing commands on this document file. Press Return. q) You should now be looking at the first sixteen lines of this document. There are a few more commands for moving down screen around the text. ^Z (try it!) moves you down a 'screen full'; up screen ^W moves up a screen full. (These letters were chosen because they are near the control key, and therefore easy to type). ^W at the top of the keyboard takes you up the file, ^Z on the bottom row takes you down the file. The last command that moves you around the text is ^X. This is a most useful jump command, because it lets you jump straight to a particular line. Typing ^X gives the prompt Jump to? The e screen editor Page 11 Enter 72, and press Return. The cursor moves to line 72. r) All this time, you will have had the help menu displayed on the screen. Once you have got the hang of the various commands, (and that takes a surprisingly short time) you'll probably want to get rid of it, and use the screen space for help menu text. Typing ^V (for Viewing the menu) will make it disappear switch - another ^V will make the menu appear again, but leave it off for the moment. s) Now you can try out the block commands. These allow you to manipulate a whole block of lines of text as a body. The block block will start with the line on which the cursor lies when commands you type the block command, ^O, and will extend either above or below the cursor line as you choose. Type ^O, and you should get a line across the top of the screen, below the Status Line, saying: Write to file, Print, Shift, Move, Copy, or Delete block ? To choose one of these options, you type its initial letter. A copy of the block may written out to a file, may be printed on your printer, may be bodily shifted to the left or to the right relative to the margins, the block may be moved to another position in the text, a copy of the block may be inserted elsewhere into the text, or the block may be deleted. To start with, try deleting a block - type D to select the Delete option. The further prompt: delete block Put cursor on line ending block and press [return] will appear. You can now use any of the cursor moving commands (left, up, right and down arrow, left word, right word, beginning or end of line, up or down a screen, as well as jump to a line, and find a character string) to move the cursor. Move it to the line where you would like the block to end - either above or below the line where you started. If your terminal has this feature, you will see the block you are selecting illuminated more brightly than the surrounding text. When you have chosen the block ending line (it doesn't matter where this is for the purposes of this tutorial), press the Return key, and the marked block will disappear; it has been deleted. The cursor finishes up on the line below the deleted block. If needed, the 'undo' key will restore the block you have just deleted. The other block commands behave similarly. Move the cursor to the beginning of the block, type ^O to start a block command, select the approriate option, then mark the end of the block. write block The 'Write to a file' option will next ask for the name of the to file file to write to (and ask for confirmation if the name you give is that of an already existing file) before a copy of the block is written to the file. print block The 'Print' option prints as soon as you define the end of the block. The e screen editor Page 12 move block The 'Move' and 'Copy' options both request that, after the copy block block has been defined, the cursor be moved to the position where the block itself (or with the 'Copy' option, a copy of the block) is to go. The 'Shift' option is a little more complicated. It is meant particularly for occasions when you want to move a block of shift block text 'sideways', ie by adding or deleting spaces or tabs at the beginning of each line in the block (useful to preserve the indentation pattern when modifying programs written in block-structured languages). After you have defined the block, the cursor will be placed at the beginning of the first line of the block. You can then type spaces or tabs, or use the DEL (RUBOUT) key to delete tabs or spaces, to get the first line in its right position. Then press Return, and the other lines in the block will follow suit, moving to the left or right in parallel with the first line. Escape and Have a go on a piece of the text and experiment will block these block commands. If you change your mind half way commands through a block command, press the Escape key. This will interrupt the command, and return you to ordinary editing. t) The command ^C allows you to examine and change the 'Edit' context and the 'File' contexts. Type ^C, and the text on the screen will be replaced by a screen showing the current Edit context. The current settings of a number of options are shown, and you can change these now you are in the Edit context. You have already come across the Auto Indent feature, which provides the indentation useful for block structured languages. auto indent Typing A will change the Auto indent option setting, turning it on or off. Similarly, typing B will change the Backup option. When you backup file the text you are editing, if this option is on, any previously existing version of the file you have been editing will have its name changed so that it ends with the extension ".BAK" (if a ".BAK" file already existed, it will be deleted first), so that you always have the last version of your text as a backup to the current version. With the backup option off, the new text simply replaces the old text in your existing file. The Tab stops option allows you to change the number of tab stops columns skipped for every tab (usually it is 8). Type T to change it; you will then be asked for the new setting. Note that this option only changes the number of columns skipped by e , and it will have no effect on, for instance, the display produced by the CP/M utility TYPE. Normally, e ignores any trailing (right hand edge) spaces or tabs that you might stick on the end of a line of text, strip since such 'white space' is usually no more than a nuisance. trailing But sometimes it is useful to be able to enter such trailing blanks white space, and the Strip option can be changed (type S) to allow this. You will have seen that the cursor position, line and column number, is displayed at the top of the screen. Some display of people find the constant updating of this position disturbing cursor or irritating, so the L option is provided to turn off (or on) position this display. The e screen editor Page 13 When a line is too long to display it all on the screen, only the first part is shown. If you move the cursor on to the 'hidden' part of the line, e shifts the whole line horizontal leftwards, thus ensuring that the part of the line on which scrolling the cursor rests is displayed. This is known as horizontal by line or scrolling. Usually, the scroll affects only the current line, page the rest of the screen being displayed as normal. Changing the H option, however, makes the whole screen scroll as a unit. This has the advantage that you can see more clearly what you are doing in relation to the rest of the text, and the disadvantage that the scroll operaton has to rewrite the whole screen, which takes time. Finally, the display shows you how many lines of text e can hold. As explained in the section above on how e works, max size of there is no limit on the amount of text e can handle at file once, but there is a (large) limit on the number of lines of text. What the limit is depends on the setting of the 'x' command line option (see below) and on the amount of memory in your computer. With the 'x' option on, or with more memory, the limit is larger. There are two more options you may choose in the Edit context: typing Return takes you back to normal editing; and F takes file you into the File context. So, for now, type F. context The File context will be displayed. It is a list of the files on the currently logged-in disk, with an indication of how much free space there is left on the disk. There are a file context number of further commands available here: commands V lets you look at another directory's files. R allows you to change the name of a file, other than the one you are currently editing. D will delete a file. C enables you to change the name of the file in which the text you are editing will eventually be saved. [return] will take you back to editing your text. u) That more or less concludes our tour through e. There entering are one or two extras to mention. Escape has one more use, to control enter control characters into the text. Type Escape and then characters a letter of the alphabet. If your terminal supports the feature, the letter will appear dimmer than the rest of the line, to indicate that it is not an ordinary character, but a control character. Now type ^Q, ^A, and ^E to exit from e , without saving the results of your practice editing. There remains only the command line options to describe. All the Edit context options and a number of further options can command be set by adding single letter 'flags', each preceded by a line dash, on the command line when you start up e. The options option flags available are: The e screen editor Page 14 -A change the setting of the Auto indent option from that set as the default (see below for how to establish the default settings for all these options). -B change the setting of the Backup option from the deafult -D this flag should be followed by a letter, in the range A to P, to indicate the drive on which e temporary buffer file should be created, if one is needed. If this flag is not given on the command line, the currently logged-in disk is used to keep the buffer file. The buffer file is only created if the file being edited is too big to fit into memory, and it is always deleted automatically before you leave the editor. If created, the buffer file will be visible as the file e$$$.$$$ in the directory displayed by the File context. Example: A> e myfile -d b -S change the setting of the Strip trailing blanks and tabs option from the default. -T this option should be followed a space and then a number to indicate the tab stop width desired. It changes the tab setting from that established by default. Example: A> e myfile -t 6 -V if by default the editor starts with the help menu displayed, giving this option on the command line will cause it to start with the help menu not displayed, and vice versa. -X normally, e saves time by using a trick to avoid CP/M doing a 'warm boot' each time you leave e. However, this takes up memory. Giving the -X flag on the command line instructs e to maximise its memory usage, and it will therefore exit with a warm boot. Setting the -X option allows an additional 700 lines or so of text to be edited. -99 a dash followed by a number (rather than a letter, as with the other options) tells 'e' to start with the current line set to that number. For instance, if you edit a file using the command line Example: A> e myprogram -34 the cursor will be placed on line 34 when you start editing. This is useful if a compiler has reported that there is a bug on that line, for example. The e screen editor Page 15 7. Implementing e on your terminal e has to be configured for the characteristics of, and the control codes used by, your terminal. This section describes how to do so. Implementation is straightforward for TeleVideo 912/920, Hazeltine 14xx, and ADDS terminals, and the KayPro portable computer, since the requisite files are provided as part of the e package. If you have a terminal made by Televideo or one which can emulate a Televideo terminal, you can pass straight on to the next section of this manual, which describes how to establish the default option settings. If you have an ADM-31, you are also in luck, because the terminal control codes this terminal uses are the same as those of the TeleVideo range - pass straight on to the next section. If your terminal is one of the others mentioned (or offers an emulation of one of them) you need to take the following two steps: 1. Change the name of the file 'eterm' supplied on the distribution disk to 'etvi', using the CP/M command: ren etvi=eterm 2. Change the name of the supplied file 'ehaze', 'eadds', or 'ekay', as appropriate, to 'eterm', thus: ren eterm=ehaze Now proceed to the next section on setting default options. Implementation on other terminals requires a passing knowledge of the programming language C, since you will have to modify one of the e program files. You will also need an editor of some kind to do the modifications. The interface between the terminal and the rest of the editor is coded entirely in the supplied file 'eterm', and this is probably the only file which will need modification to suit e to your terminal. 'eterm' is supplied configured for a TeleVideo. 'eterm' includes extensive comments describing the terminal interface to help you with any changes which may be needed. Before starting configuring 'eterm', you should have to hand the terminal manual to guide you on the control codes to use. You will need to establish what codes should be sent to the terminal to perform the following functions: * put the cursor on any specified position on the screen ('cursor addressing') * clear the line from the cursor position to the right hand edge of the screen to spaces (clear to end of line) * delete the line on which the cursor is resting, and move following lines up one (delete line) * delete the line containing the cursor and all the lines below it to the end of the screen (delete to end of page) * insert a blank line at the cursor line, moving the cursor line and lines below down one (insert line) * if available - start and stop displaying characters in 'dim' or half- intensity mode (note that these are optional, and will only work properly with e if they do not themselves take up space on the screen). The conventional names for these operations are those given in brackets. The e screen editor Page 16 Using the C functions provided in 'eterm' as a guide, new functions to implement these terminal control sequences should be written and edited into 'eterm'. Next, you need to determine which keys should be used to request each of e's commands. It is as well to keep to the command - key correspondences normally used by e, at least to start with, although you may want to take adavantage of any special keys offered on your terminal's keyboard. The first step is to alter the help menu so that it is appropriate to your key selections. At the end of the file 'eterm' is the C function which provides the help menu. Edit this to make it correspond to your selected command-key choices. Note that the vertical bar included in the help menu text is not displayed as part of the menu - it is used to signal a change from dim to bright (half to full intensity) text and vice versa (if you have not implemented the codes to change intensity, the vertical bar character is ignored in displaying the help menu). Finally, modify the key translation table to be found in C function keytransalate (located immediately above the help menu function). This table converts the codes sent by your terminal in response to key depressions into the internal codes used by e to represent editing commands. Some terminals send two codes when certain keys are depressed: a 'lead in' character, followed by a character to indicate which key was pressed. There are comments in the keytranslate function about how to deal with such cases. e assumes that the terminal's display screen is 80 columns wide and 24 rows deep. If your screen is smaller (eg 64 by 16), you will need to (a) edit the help menu to fit it into the smaller width; (b) reduce the width of some of the command prompts (these are scattered about the program text); and (c) change the values of the defined constants SWIDTH and SHEIGHT. These two constants are defined in the header file 'e.h', and should be set to one less than the terminal screen width, in columns, and height, in rows. If your screen is larger than 80 by 24, adjust SWIDTH and SHEIGHT appropriately. The help menu will probably not need changing. Note that e has not been tested with screens of size other than 80 by 24. 8. Changing the default settings of the options The options settable using flags on the command line each have a default value defined in the 'main' function of e. This function is to be found in the supplied file 'e', and is clearly commented and marked out. You will probably not need to change any of the default option settings, at least until you have got used to using the editor. You amy also want to set the value of CURSORWAIT, defined at the top of file e.h, to suit the clock rate of your microprocessor. This just affects the speed at which the cursor flips between brackets and between the Replace? prompt and the string to replace in the Alter command, so getting CURSORWAIT right is not vital for the operation of the editor. The e screen editor Page 17 9. Compiling and loading e e is written in the programming language C, and was developed using the BDS C compiler for CP/M, version 1.50a. It is not recommended that you use versions of BDS C earlier than 1.46 - e uses facilities that were introduced with 1.46. With other C compilers, you will need to do some preliminary work to make the source code compatible. There may be trouble with the setjmp() and longjmp() library functions, and with the file i/o. You are warned! The following files make up the e package: e.doc this file e.sub a command file to compile and load e l2.com Mark of the Unicorn's space saving loader (included here for convenience - e MUST be loaded with this loader, not with the standard BDS C loader, clink) e the first program source file for e - contains the 'main' function (and others) e1..e10 the rest of the source code eterm the terminal interface functions (supplied set up for a TeleVideo terminal) ehaze the same as eterm, but set up for a Hazeltine terminal eadds ... for the ADDS range of terminals ekay ... for the KayPro portable computer e.com the e editor, compiled and loaded, for a TeleVideo terminal To compile and load the editor, it is best to PIP the following BDS C compiler files onto the disk containing the above files (only these files are needed): cc.com cc2.com c.ccc deff.crl deff2.crl Then put the disk in drive A: and use CP/M's SUBMIT utility with e.sub to do all the work. The compilation and loading will need about 300K of disk space. If you don't have that much to spare, you can move e.doc elsewhere first, to save about 40K. The e.sub file specifies the address the C compiler is to use as the location of the bottom of the external data area, and the address where the stack is to start. These addresses should allow about 400 bytes of stack space (which is just enough). The stack space is reported by the L2 linker at the end of the link. The remaining memory from the stack top to the base of CP/M is used as work space to store pages of the text being edited. If you are using other versions of BDS C, a complex 'eterm' file, or other compilers, you will probably have to change these addresses. Try to keep them as low as possible, whilst still not allowing the data and program areas to overlap, and keeping about 400 bytes of stack space. The addresses are defined in the '-e' option to the cc compiler, in the '-t' option to the L2 loader, and in the header file 'e.h'. The e screen editor Page 18 If you need to change these addresses, be sure to make all the following amendments: . change the address of the external data area specified to the compiler, by altering the -e option setting for all cc compiler comands in the command file 'e.sub'. . change the address of the 'top' of the data area, specified in the -t option to L2 in the file 'e.sub'. . change the value of the #defined constant TOP in file 'e.h' to match the L2 -t option