CTSS: ED and friends: online editors

The first disk-based text editor on CTSS was invoked by either of the commands INPUT and EDIT, the first creating a new file for insertion and editing, and the second for editing an existing one. These worked only on card image files and would automatically number the sequence iDs for you. Actions were limited to entering text and either replacing or deleting the contents of a card/line by referring to its sequence number.

A more advanced, context aware editor called ED was introduced later, based on concepts and commands introduced in the TYPSET text processing system (which we will look at it a later post).

None of these editors are available on the CTSS we have today, However, we do have two editors which were developed after ED with a similar interface, EDC for card image files and EDL for line marked files.

There are different commands for card image (EDC) and line marked (EDL) files and you need to select the correct one based on the file you are editing. See Files and Directories for a discussion of the two formats; if you are looking at an existing file and are not sure of the format, try running P on it: if it shows sequence numbers, use EDC.

Invoke the editor by giving the name of the file you want to work on, eg EDL HELLO MAD. If the file does not exist, it will create it.

If you have interrupted a previous editing session you may see a message like Old file (INPUT 5 --Do you wish to delete it?; it's safe to reply yes.

The editors have two modes, input where you can type lines and edit where you can give commands. New files being edited will start up in input mode, existing files in edit mode. Press Enter at the start of a new line to switch between the two.

Edit mode commands have a long form and an abbreviation which we will show in brackets in the discussion below.

In edit mode, typing file (fl) will save the file and exit the editor. Giving a parameter will save it under a new name.

The quit (q) command will exit without saving.

Here's what this looks like when I edit a new file, add text and then save and exit:

edl try mad
W 1847.7
 FILE    TRY   MAD NOT FOUND.
Input:                       
	PRINT COMMENT $HELLO FROM ED$
	END OF PROGRAM

Edit:
file 
*
R .016+.016

Note the blanks at the start of the PRINT and END program lines; these were introduced by pressing Tab. ED knows the correct indentation for the languages used on CTSS.

The blank line after END OF PROGRAM tells ED to go to Edit mode, after which I give the file command to return to the command level.

The editor maintains an internal pointer on which line it is on in the file.

The command top (t) and bottom (b) move to the start and end of the file. next (n) will move one line down, or you can give it a numeric parameter to move down a certain number of lines.

locate (l) takes a string as a parameter and finds the first line starting at the pointer where the string matches. It will print the line if found and move the pointer, otherwise it will print an error message.

Type print (p) to show the current line you are on. You can give this a numeric argument to print more than one line.

A simple way to print the whole file is to move to the top with t and then typing something like p 1000.

Pressing Enter while in edit mode will switch you to input mode. Type lines of text, which will be inserted after the current line pointer, and then type Enter at the start of a new line to return to edit mode.

While in edit mode, use the command insert (i) followed by a line of text (ie without pressing enter before the text) to insert a single line and remain in edit mode.

retype (r) followed by a line of text will replace all of the current line. delete (d) will delete it.

change (c) will replace parts of the line by matching text. An example that will replace the word "from" with "to" on the current line.

c /from/to/

The / are delimiters and can be replaced with any character that is not in the search or replace text.

change takes two parameters: number of lines and g. The first specifies how many lines to search forwards and do replacements. The second is a flag meaning global, if set it will replace all instances of the from text on each line.

So to replace every instance of "before" to "after" in the whole file you could do:

c QbeforeQafterQ 1000 g

EDC has special handling for card sequence numbers, which normally occur in columns 76-80.

The ncols (nc) command determine how many columns are available for non sequence number text, and is normally set to 72.

serial (sr) normally takes two parameters, m and n, indicating the start sequence number and the increment. Normally these are both set to 10, so you will get sequence numbers 00010, 00020 etc. serial off will turn off sequence number generation; this can be restored with serial on.

Note the EDC will automatically resequence the numbers in an existing file unless you specify serial off before you start.

See the CTSS Programmer's Guide p333 for the common set of ED commands and then p351 and p372 for adjustments made to EDL and EDC respectively.

I welcome any questions or comments, and also especially any corrections if I have got something wrong. Please email me at rupert@timereshared.com