COMMENT ⊗   VALID 00013 PAGES
C REC  PAGE   DESCRIPTION
C00001 00001
C00002 00002	ON THE USE OF THE DATAMEDIA TERMINAL.
C00007 00003	CONNECTING TO THE AI LAB COMPUTER.
C00012 00004	FILE DIRECTORY INFORMATION.
C00017 00005	EDITING A FILE.
C00021 00006	COMMANDS WHICH EDIT FILES.
C00025 00007	PRINTING A FILE.
C00028 00008	APPENDIX A.   PLUGGING IN A DATAMEDIA TERMINAL.
C00034 00009	CURSOR OPERATIONS.
C00037 00010	LINE OPERATIONS.
C00041 00011	TEXT-MOVING OPERATIONS.
C00045 00012	APPENDIX C.  INTERPRETING AI LAB DOCUMENTATION.
C00048 00013	APPENDIX E.  WHAT TO DO IN CASE OF TROUBLE.
C00052 ENDMK
C⊗;
ON THE USE OF THE DATAMEDIA TERMINAL.
This is file TYPE.DM[1,RWF] at the Stanford AI Lab (SU-AI), last written
August 13, 1979.  Bob Floyd (aka RWF) wrote it, maintains it, and welcomes
suggestions.


STARTING UP.
 
The DataMedia terminal consists of a keyboard, a TV-like screen, and a
telephone.  (If it is not plugged in, see Appendix A.)  Near the back right
of the screen unit are two knobs and the ON-OFF switch.  Turn the switch on
and wait for the screen to warm up.  A blinking line, called the cursor (or
sometimes the arrow), should appear in the upper left corner of the screen.
Adjust the contrast knob until it does.  Then adjust the brightness knob so
that the white background just disappears.  The contrast knob can then be
adjusted for visual comfort.  If the above fails to work, see the file
DMINT[INF,CSD] for diagnostic information.

Set the rate selection switch below the screen to SEL (marked 1200/150 on some
terminals).  If the FULL DUPLEX light is off, turn on using the DUP key on the
keyboard.

The knob on the right side of the keyboard controls the volume of the
terminal's bell (actually a beep).  Start the knob off in the middle position.
You may later want to turn it toward you for a quieter bell or away for a
louder.  The system uses the bell to get your attention.


THE KEYBOARD.
 
The keyboard contains three types of keys.  Some keys send their character to
the computer.  Others, while held down, change the meaning of the character
keys.  The third type switches the terminal into a new state.  Most of the
keys belong to the first category of characters.  The following keys modify
the meaning of the characters typed while they are held down.  
(1)  SHIFT.   Hold this key down like the SHIFT key on a typewriter for upper
     case letters and for the top character on keys which show two characters.
     Without the SHIFT key, the bottom character is typed.
(2)  ALPHA LOCK.   Press this key to go from typing upper case letters to 
     lower case or vice versa.  It affects only letters.
(3)  EDIT and CONTROL.   These keys, which may be held down while a character
     is typed, modify the meaning of that character in various ways, some of
     which will be described in detail later.  To say briefly, "Hold down 
     EDIT while typing  D ", this document uses EDIT<D>.

Some keys are marked with a word or a syllable, such as RETURN.  Be sure to
use the RETURN key when called for, and not to type the six letters
separately.

The HOLD key may be used to stop, and to restart, the terminal display if it
is typing too fast for you to read.  The CALL key may be used to interrupt 
anything that is going on that you want stopped, such as the display of a 
long text.

CONNECTING TO THE AI LAB COMPUTER.
 
If you do not already have them, get a project name, progammer initials, and
password from Les Earnest or Denny Brown.  After your account has been
activated, you may use the AI computer.  Turn on the power as described above.
Set the PHONE/MODEM switch on the front of the monitor to PHONE and pick up 
the phone.  From a campus extension, to avoid telephone charges, dial 7-0081.
From off campus, dial 493-1422.  The computer will answer with a beep.
Quickly set the PHONE/MODEM switch to MODEM and hang up the phone.  If the 
lines are busy, see Appendix D for an alternate connection method.  The
terminal is now connected to the computer.  Press the CALL key.  The system
monitor will begin a new line with a period, which shows that it awaits your 
command.  (If it fails to do this, the computer is probably not in service.)  
You must first identify yourself to the system by "logging in".  Type  L YYY
or  L XXX/YYY  followed by a RETURN where  XXX/YYY  is your project name and 
programmer initials.  When the system prints  PASSWORD= , type your password.
It will not appear on your terminal.  The system will now print a set of 
messages to all users of the AI system, not all intelligible.  If you log in 
using a comma to separate your project from your initials, all current 
messages, including those you have seen before, will be printed.  For more 
information on logging in, type  HELP LOGIN  followed by  RETURN .  If you 
mistype your identification and the system types a TRY AGAIN message ending 
with the  # sign, retype the XXX/YYY and RETURN part.

After logging in, type TTY DM RETURN to tell the system that you are using
a DataMedia terminal.  To make this happen automatically, see below (COPYING 
A FILE) for details on setting up an OPTION TXT file.


DISCONNECTING FROM THE AI LAB COMPUTER.
 
When you get through using the computer, follow this disconnecting procedure
in order to release the phone line for other users.  When the monitor prints
the period (.), type  K RETURN  to tell the system that you want to quit.
(To get back to the monitor, if you are editing, type  EDIT<E> .)  The  K
stands for  KILL JOB .  The system will then print accounting information
and KJOB.  Now hold down and release the BREAK key to turn the MODEM light
off.  Set the PHONE/MODEM switch back to PHONE and turn off the power.


CORRECTING INPUT.
 
When typing at the terminal, you may make corrections at any time until hitting
the RETURN key.  Corrections are made where the cursor is.  To move the cursor
right or left, type EDIT<SPACE> or EDIT<DEL> respectively.  To change the
character at the cursor, type the new character.  To delete the character
at the cursor, type  EDIT<D> .  To insert characters at the cursor, type
EDIT<I>  followed by the desired characters, using  EDIT<SPACE> to stop
inserting.  When the line is correct, type RETURN.

FILE DIRECTORY INFORMATION.
 
To see the names of all your files, type  DIR RETURN .  To see the names of
another user's files, type  DIR[XXX,YYY] RETURN  where  XXX,YYY  is the
project name and programmer initials of that other user.


FILE NAMES.

Your own file names are of the form NNNNNN.EEE, where NNNNNN is a name of up to
six letters, and EEE is a code for the kind of file.  You might let EEE be TXT
for English text, DAT for numerical data, etc.  The name for someone else's 
file is NNNNNN.EEE[XXX.YYY], where XXX.YYY is his project name and programmer
initials.
 

COPYING A FILE.

(In this section,  <-  is used to stand for the left-pointing arrow on the
keyboard.)  To make a copy of a file, use the COPY command in the form 
COPY newfile<-oldfile RETURN , to create a file whose name is  newfile , in
your area, which is a copy of the file named  oldfile .  If you have not
already done so, you should type  COPY OPTION.TXT<-OPTION.TXT[1,DPB] RETURN ,
creating a new file in your area called OPTION.TXT, a copy of a file by the 
same name belonging to programmer DPB.  This file contains monitor commands 
which will automatically be executed whenever you log in in the future and 
which tells the system that you are using a DataMedia terminal.  To practice
editing a file, type  COPY DMUSE<-DMUSE[INF,CSD] RETURN  and then
ET DMUSE/2P RETURN , and follow the directions which will appear on the 
screen.  When done editing, type  EDIT<E> .


READING A FILE.

Type  ET filename RETURN , where  filename  is the name of the file you want
to read (see above for file names).  Files are broken up into parts called
pages.  To see the next screenful of information in a page, type  CTRL<L> .
To back up within a page, type  CTRL<K> .  To get to the next page, type
EDIT<P> .  To go forward  n  pages, type  EDIT<+nP> ,  To go backward  n 
pages, type  EDIT<-nP> .  To go to page  n , type  EDIT<nP> .  When you are
done reading, type  EDIT<E>  to return to the monitor.  You can use these
operations, and those in DELETING FROM A FILE, to read your mail, which is
on a file named  \M .


CREATING A NEW FILE.

Type  CET filename RETURN .  Then type the lines of text you want 
to go into the file.  To start a new file page (for example, just
before a new subject heading), type  EDIT<X> MARK RETURN .
When the file is complete, type  EDIT<E> .

EDITING A FILE.

While reading or creating a file (see above), you may make changes to
it by addition, deletion, or replacement.  The following sections tell
how.  By the current line, page, or file, we mean the one the cursor is in.

In addition to the operations listed under READING A FILE, you will need to
know these:
	To move the cursor down or up  n  lines, type
		EDIT<n> RETURN  and
		EDIT<n> DEL  respectively.
	If  n  is  1, just type  RETURN and DEL respectively.
	To see more of the text at the top or bottom of the page, type
		EDIT<T>  or EDIT<B>  respectively.
	To move the cursor to line number  n  of the current page, type
		EDIT<nL> .
Other operations are in APPENDIX B.
 

ADDING TO A FILE.

To add material at the end of any page of a file, read that file with the
cursor at the line of asterisks which ends that page.  If you are not already
reading the file, type  ET filename/nE RETURN , where  n  is the page number.
Then type in the new lines to be added to the file.

To insert new lines in a file, read that file with the cursor at the desired
place of insertion.  Type  EDIT<NUL RETURN> .  Then type in the new lines.
When finished, type  EDIT<RETURN>.

To insert new material in a line of a file, read the file with the cursor at
that line.  Then use the methods described in CORRECTING INPUT, above.


DELETING FROM A FILE.

To delete a page of a file, read the file with the cursor in that page.
Pages are divided into messages, each beginning with a bold letter  O .
Type  EDIT+CTRL<O> EDIT<NUL D> .  Each time you do so, the message the cursor
is in will be deleted.  When every message in a page is deleted, so is
the page.  Use this while reading your mail, to delete a message from your
mail file.  Your mail is on the file named  CTRL<O>  (letter  O , not zero).

To delete one or more lines from a file, read the file with the cursor at the
first line to be deleted.  Type  EDIT<n NUL D> , where  n  is the number of
lines to be deleted.  You may omit  n  if it is  1 .

COMMANDS WHICH EDIT FILES.
 
CET filename RETURN.   This command (Create and Edit) creates a new file 
	called  filename  containing a directory page and blank page.
ET filename RETURN.   Begin editing an existing file called  filename .
	The screen will display the text of a short file or the directory
	page of a long one.  If the filename is omitted, the most recently
	edited file is assumed.

To protect the file from accidental change, follow the  filename  with  /R .


SENDING MAIL.

To send a message to another person, create a file page which contains the
message (not forgetting a RETURN on the last line), then, while reading that
page, type  EDIT<X> MAIL yyy  where  yyy  is the programmer initials of the
person to whom you are sending a message.  Use a list of such initials,
separated by commas, for multiple addressees.  See file MAIL.BH[UP.DOC].

To reply to mail from programmer  yyy , while reading it, add your reply to
the page you are reading in the mail file, or to a new page, then send the
page as above.

To retain a copy of all mail you send, create a file called  OUTGO.MSG  and
copies will automatically be put there.  You may edit  OUTGO.MSG , for example
to remove old messages.

To send a one-line message to  yyy , type  
	SEND yyy message RETURN
or (while editing) type
	EDIT<0X> SEND yyy message RETURN

To find out John Doe's programmer initials, type
	FINGER JOHN DOE RETURN.

For information from the AI phone directory, type  FIND string RETURN  to
print all the entries in the directory which contain  string , which might
be a name, phone number, etc. For information from the Computer Science
Department directory, type
	FIND string IN PEOPLE.DAT[PER,CSD] RETURN.
In fact, FIND can be used to look for  string  in any file.

If programmer  yyy  is at another computer center (say SUMEX), type 
yyy%SUMEX  in mail commands.

PRINTING A FILE.

To make a hard (paper) copy of a file on the XGP printer at SAIL, type
	XSP/J filename RETURN
The  /J , standing for Jacks Hall, will result in delivery to the OUTPUT FROM
THE AI LAB mail box in Jacks, in about a day.  A header page will give your
name and other identifying information.
 
Use  CTRL< <- O > as the filename in the XSP command to print your mail file.

To get hard copy from a Diablo terminal, log in at that terminal and type
	TYPE/PAU filename RETURN

Use  CTRL(<-O)  as the file name to print your mail file.


TO COPY AND JOIN PARTS OF FILES.  (See above, COPYING A FILE, first.)
 
Examples:
COPY f1<-f2 RETURN
	creates a new file  f1 , which is a copy of file  f2 .
COPY f1<-f2(3:5) RETURN
	f1  is a copy of pages 3 through 5 of  f2 .
COPY f1<-f2(2:4,16,11:14) RETURN
	f1  is a copy of pages 2-4, 16, and 11-14 of  f2 .
COPY f1<-f2,f3,f4
	f1  is a copy of files  f2 , f3 , and  f4 , joined together.
COPY f1<-f2(3:5),f3,f4(6)
	f1  is a copy of pages 3-5 of  f2 , then  f3 , then page 6 of  f4 .


TO PRINT PARTS OF FILES

The file name in a printing command,  (XSP, TYP, etc.)  may be followed by
a parenthesized list of page numbers, and only those pages will be printed.
See the examples of copying parts of files.


TO DELETE A FILE.

(Be careful with this one; be sure you have the right file name, and that 
you no longer need the file.)  Type
	DELETE filename RETURN


APPENDIX A.   PLUGGING IN A DATAMEDIA TERMINAL.
 
Plug the terminal jack at the end of a cable labeled LINE, from the back of
the screen, into any telephone outlet.  Into the terminal jack, plug the jack
of any telephone.  Plug the keyboard cable into KEYBOARD in the back of the
screen.  Plug the power cord from the back of the screen into any grounded
110V outlet.



APPENDIX B.   LIST OF USEFUL EDITING OPERATIONS.

Comments to Art. Samuel = ALS.  Fuller documentation on  E.ALS[UP,DOC] .

Files are broken into pages by page marks, which appear on the screen as
lines of asterisks.  Pages may be broken into messages, by lines which
begin with a boldface  O .  Pages, or messages, may be broken into paragraphs
by blank lines.  In the editing operations below, we use  n  to stand for a
number.  In some commands, the number may be omitted if it is  1 ; if so we
use  n1  to stand for the number.  In some commands, one may use  !  instead
of a number to mean the number of lines to the end (or beginning) of the
current paragraph, or  CTRL<O>  to mean the number of lines to the end or
beginning of the current message; if so, we use  nn  to stand for the number.
If both alternatives to the number are allowed, we use  nn1  to stand for
the number.  Usually,  CTRL<N>  can be used as the number to do something
as many times as possible.

The  CET  and  ET  commands may be modified by putting one or more of the
following modifiers, called switches, immediately after the file name to
which they apply.

/E	Open the file with the cursor at the end of the file.
	(Use this to add stuff at the end of the file.)
/nE	Open the file with the cursor at the end of page  n , where  n  is
	any number.  (Use this to add stuff at the end of a page.)
/F	Break the file into pages small enough to be shown on the screen.
/nF	Break the file into pages of at most  n  lines.
/nP	Open the file displaying page  n .  (Use this and  /nL  to get to
	a particular place in the file.)
/nL	Open the file with cursor at line  n .
/R	(Meaning READ ONLY.)  Protect the file from modification.

To protect the file from accidental change, follow the filename with  /R .
CURSOR OPERATIONS.

Moving cursor among pages.
EDIT<P>		cursor to next page.
EDIT<-P>	cursor to previous page.
EDIT<+ n1 P>	cursor forward  n1  pages.
EDIT<- n1 P>	cursor back  n1  pages.
EDIT<nP>	cursor to page  n .

Moving cursor within a page.
EDIT<nn1> RETURN	cursor forward  nn1  lines.
EDIT<nn1> DEL		cursor back  nn1  lines.
EDIT(>) 		cursor forward  4  lines.
EDIT(<)  		cursor back  4  lines.
EDIT+CTRL<]>		cursor forward 12 lines.
EDIT+CTRL<\>		cursor back 12 lines.
EDIT<n1 L>		cursor to line  n1 .
EDIT<+ n1 L>		cursor forward  n1  lines.
EDIT+CTRL<N> EDIT<L>	cursor to last line.
EDIT<- n1 L>		cursor back  n1  lines.
EDIT<n1> EDIT+CTRL<D>	cursor to  n1 -th line from top of window.
EDIT<n1 NULL HOLD>	cursor to  n1  line up from bottom of window.
EDIT<X> LINCNT RETURN	terminal tells you how many characters are in
			current line and page.

Moving cursor within a line.
EDIT<n1 SPACE>  to move cursor right  n1  places.
EDIT<n1 DEL>  to move cursor left  n1  spaces.
EDIT<TAB>  to move cursor to right end.
EDIT + CTRL<L> to move cursor to left end.



CHARACTER OPERATIONS.

Changing characters at the cursor:  Type the new characters you want over the
old ones.

Inserting new characters at the cursor:
(1)  Type  EDIT<I> .
(2)  Type the characters you want to insert between the existing characters
     at the cursor.  No other editing operations will work, until you
(3)  Type  EDIT<SPACE> or other cursor-moving operation.

Deleting characters at the cursor.
EDIT<n1 D>	deletes  n1  characters starting at the cursor.
		At end of line, deletes carriage return, joining two lines.
EDIT<K>c	deletes all characters from the cursor up to the next
		occurrence of character  c .  If  c  is RETURN, deletes
		the rest of the line.

Cancelling changes in the current line:  ESC .

LINE OPERATIONS.

Inserting new lines in the file.
(1)  Type  EDIT<NUL RETURN> .
(2)  Use cursor-moving operations to get to the places where you want to
     insert lines.  At each cursor location, you can type new lines which
     will be inserted between the old ones.  No other editing operations
     will work, until you
(3)  Type  EDIT<RETURN> .

Deleting lines at the cursor.
EDIT<nn1 NUL D>  deletes  nn1  lines.  (If an entire page is deleted, pages
		are renumbered.)  At end of page, deletes page mark to
		combine pages.
EDIT<X> CANCEL RETURN   cancels an erroneous deletion.

Looking at different lines of the file without moving the cursor.
EDIT<J>		look below cursor.
EDIT<0J>	look around cursor (number zero).
EDIT<-J>	look above cursor.
EDIT<T>		see more at top.
EDIT<B>		see more at bottom.



MATCHING OPERATIONS.

Finding occurrences of string  s  in a page, starting from the current line,
going down, and continuing around from the top after hitting the bottom.
(1)  If you want to find  s  only where it appears surrounded by blanks or
     punctuation (like FIND in this sentence), type  EDIT<NUL> ; otherwise
     the editor will find  s  even if it appears as part of a larger word.
(2)  To search the current page, type  EDIT<F> ; otherwise, to search the
     whole file, type  EDIT<X> F  and one blank space.
(3)  Type the string  s  you want to search for.  (Any further spaces you
     type will be taken as part of  s .)
(4)  Type  RETURN  to initiate the search.  (To search the directory
     instead of the body of the file, type  EDIT<P> .)
(5)  To repeat this search, as many times as desired, type  EDIT<NUL *> .

To find occurrences of string  s1  and replace each one with  s2 , use the
command for finding string  s1  (see above), but after  s1 , type  EDIT<\> s2 .
To repeat such a substitution  n1  times, after having done it once, type
	EDIT<n1 NUL \>
To repeat it as many times as it can be, use
	EDIT+CTRL<N> EDIT<NUL \>
To make changes to the string that has been found or substituted by the above
commands, you may want the cursor to be left under the string ready to edit 
the line.  To do this, on a first search, type  EDIT<RETURN> .  To repeat a
search, type  EDIT<*> .  To repeat a substitution, type  EDIT<\> .

TEXT-MOVING OPERATIONS.

Moving a part of a file page to a new place.
(1)  (A)  To move the text without leaving a copy behind, type  EDIT<n1 A>
	  to pick up the next  n1  lines with the cursor.  Otherwise,
     (B)  To move a copy of the text, leaving the original behind, type
	  EDIT<n1 C>  to pick up a copy of the next  n1  lines with the
	  cursor.
(2)  Use the cursor-moving operations (or matching operations) to take the
     cursor where you want the text to go.
(3)  (A)  To drop the text into the current cursor location in the file,
	  type  EDIT<E>  (which has this meaning only if there are lines
	  attached to the cursor).  To make more copies, return to step (2).
	  Otherwise:
     (B)  To discard the attached lines, type  EDIT<NUL K> .

Writing a modified page back to disk:  EDIT< . > .



MARKING OPERATIONS.

Marking ends of pages.
EDIT<X> MARK RETURN	makes a page start at the cursor.
EDIT<X> DELETE RETURN   removes page mark at end of current page.

To put "bookmarks" on lines for later reference.
EDIT<NUL M>		mark current line.
EDIT<NUL - NUL M>	erase mark from current line.
EDIT<n M>		move cursor forward to n-th mark.
EDIT<-M>		move cursor back one mark.

SWITCHING BETWEEN FILES.

EDIT+CTRL<F> filename RETURN
	switches to reading and editing  filename .
EDIT+CTRL<H> filename RETURN
	switches to (only) reading  filename .
EDIT<?>
	switches to reading instructions for the editor.  (Warning -- they
	are written for the DataDisc terminal users.)
EDIT<H>
	switches back to previous file.
EDIT<n> EDIT+CTRL<F>
	switches to reading and editing the n-th file used since login,
	at line where you left it.
EDIT<n> EDIT+CTRL<H>
	switches to (only) reading the n-th file used since login, at
	line where you left it.
EDIT+CTRL<U>
	lists file names and numbers for use in the above two commands.

APPENDIX C.  INTERPRETING AI LAB DOCUMENTATION.
 
When reading documentation for AI Lab material, it will often be necessary
to transcribe it into the characters available on the DM keyboard.  If a
symbol appears preceded by a boldface  b , you should not type the  b ,
but type the symbol with the EDIT key held down; 
	bE   means   EDIT<E>
If a symbol is preceded by a boldface  c , you should not type the  c , but
type  EDIT<NUL>  before the symbol;
	cE   means   EDIT<NUL> E
If a symbol is preceded by both,
	bcE   means   EDIT<NUL E>
If a symbol other than  b  or  c  appears in boldface, type it with the
CTRL key held down:
	boldface d    means   CTRL<d>
	boldface bd   means   EDIT+CTRL<d>

(On the AI Lab's Data Disc terminals,  b  and  c  are known as CTRL and META
respectively.  Watch out for the fact that the CTRL keys in the two terminals
do not correspond.)



APPENDIX D.   ALTERNATE CONNECTION TO THE A.I. LAB COMPUTER.
 
Use phone number 7-1112 or 493-3280.  After switching to MODEM as you 
would for the other numbers, type
	@R RETURN
Wait for a response.  Then type
	@O 11 RETURN
(Letter O).  Wait for a period.  Then type
	TTY DM RETURN
Then log in as usual.  When done, log out as usual.  For more detail, see
DM.ME[UP,DOC] , particularly "Use of DMs via TIPs".
APPENDIX E.  WHAT TO DO IN CASE OF TROUBLE.
 
When the terminal is typing things faster than you can read them:  press the
HOLD key once.  The terminal will stop, displaying the word HOLDING.  Press it
again to restart the printing.

When you have made mistakes in controlling the editor, and it doesn't seem to
understand you:  type  EDIT<RETURN> .  If that doesn't work, use  EDIT<E> .

When you want to stop whatever the terminal is doing (for example, printing a
long file at you that you don't want to see):  press the CALL key.

When you want information about how to use a feature of the system: 
type HELP RETURN  for a list of such features.  Type HELP f RETURN  for
information about feature  f .  The available HELP features include:
	MAIL (alternate mailing technique)
	LOGIN
	LOGOUT (alias KJOB)
	DIR (directory of files)
	FIND (to find a word in a file)
	FINGER (to identify someone by name or by user ID)
	E (Documentation on the editor)
	ETEACH (Instruction on how to use the editor; take together with
		Appendix C of this document)
	TALK (with other current terminal users)
	YUMYUM (restaurant guide)
	UNDELE (to rescue a file you deleted)

When you want to clear garbage from the screen:  try  NUL -P .  If you are
in the editor, an additional  EDIT<V>  may be needed.  If all else fails,
get help or turn terminal off and on.



APPENDIX F.   SOME USEFUL FILES.
 
CSD.BBD[INF,CSD]  (page 2)  General information about CS department files.
PEOPLE.DAT[PER,CSD]  CSD personnel directory.
\M	Your mail file.
\B	AI Lab Bulletin Board.
\NE	News Summary.
\C	CSD Bulletin Board.
\DA	Messages of the day.
\DA	News Digest.
\F	Forwarding addresses for computer mail to departed people.
\G	Gripes about computing equipment.
\NO	Current login notices.
E.ALS[UP,DOC]  is a reference manual for the editor.  To read it while
	editing, type  EDIT<?> .  To return to editing, type  EDIT<H> .