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Notes on Eperror\ra Greg Lee, 9/84
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  On those rare occasions when EP detects an erroneous formatting command,
it will chain to EPERROR.COM, provided it can find this file on the
current default disk. After Eperror has been called, the two most frequently
exercised options will be ^C, to exit, or `e<CR>' to edit the file that
was being formatted. But there are others.

  First, a few words about `e' for edit. The idea is to have an economical
way for you to call up your own text editor, so all this does is call up
the editor and supply the name of a text file. If the `e' is followed
immediately by a carriage return, the name supplied to the editor will
be that of the "principle" file that was being printed. This is the
name that was given right after `EP' when EP was originally called. When
you are using imbedded files, this might not be the file in which the
problem arose. Fortunately, the `e' command can also be followed (immediately)
by the name of the file you would actually like to edit.
  The initial assumption is that your editor has the file name `E.COM'.
If that is not so, this assumption can be changed by placing the name
into the initialization file `EP.INI', by going through the following
procedure:
	(1) if eperror has not already been called, call it with
		A>eperror
	(2) load a fresh copy of EP.INI with `l<CR>'
	(3) use the `$' command to enter the name of your editor -- e.g.
	    if the editor's file name is WS.COM, type `$ws<CR>' (don't
	    include the extension)
	(4) save the updated EP.INI with `s<CR>'

In step (1), if Eperror is called independently, and the last program that
you ran under CPM was not EP, Eperror's attempt to characterize the error
that occurred and to list the line where it was found will produce some
junk on the screen.

  Now for the other options. Eperror can be used to browse though the
data area that EP has just been using, and also to change the default values
assumed for command variables (page-length, bottom-margin, and so on).
I don't know how much use this will be to you -- probably not much. As to
browsing, Eperror has screen prompts that say how to look at what. If you
are making extensive use of your own variables and macro commands, it
might be helpful to look at the current variable values with the `\'
command.

  As for changing default values, you might find it more straightforward
to do this through EP by use of the \save command (cf. EPREF.DOC). But if
you choose to use Eperror, the procedure is much like that given above
for changing the editor's name, except that step (3) would involve using
the `=' command to patch in new default values. The value typed in after
`=', by the way, can be a decimal number, a hex number followed by `h',
a character, or nothing (in which case 0 is assumed).
  One sort of change to the defaults that you would need Eperror for is
this: within EP.INI are codes for the types of EP commands, like whether
they have arguments which are horizontal measures, and whether they cause
breaks. In this last regard especially, you might find some of the
choices I have made inconvenient. Or you might want to type some of your
own variables. To change a type, obtain the memory address and the current
value with the `t' command, then enter your new choice using `='. Here
are the meanings of the bits in the coding:

	bit 0	takes `h' type argument -- numerical value, horizontal measure
	bit 1	takes `v' type argument -- numerical value, vertical measure
	bit 2	synonym of Epson command -- value is character to turn on
					an Epson print mode
	bit 3	causes a break
	bit 4	takes `c' type argument -- character value
	bit 5   value is special character to be placed in output line
	bit 6	value is pointer to string
	bit 7	causes a break before next input line
	bits 5 and 1 together
		assume argument=1, don't scan for a numerical argument

Among the "special" characters associated with bit 5 are some internal
codes, as follows:

	90H	center the following
	91H	right adjust the following
	92H	wide space
	93H	wide space with absolute width
	94H	pause here for console input
	95H	place wide space here (from use of \hfill)
	96H	back space


  And finally, for reference, here is the overall format of the initialization
data kept in EP.INI:

			load
 type	symbol		addr size

 word	val[27][27]	4906 05B2 values of `pl', etc.
 byte	valtp[27][27]	4EB8 02D9 type of value, e.g. numerical
 byte	modelen[64]	5191 0040 width of Epson built-in char's, for each mode
 byte	pmlen[256]	51D1 0100 width of Epson proportional char's
 word	mode		52D1 0002 16 bits keep track of font, etc.
 byte	(not used)	52D3 0001
 byte	bending[7][24]	52D4 00A8 data for \bend command
 byte	editname[10]	537C 000A name of editor called by eperror
	(end)		5386
		total = A80H bytes, 10 pp. or 21 records