00100	Appendix A
00200	
00300	
00400		This paper was given at a conference on "Man and the Computer"
00500	sponsored by Institut de la Vie of Paris and held in Bordeaux in
00600	June 1970.  Regrettably, the proceedings of the conference have not
00700	appeared almost three years later.
00800	
00900	                    THE HOME INFORMATION TERMINAL
01000	
01100	                          by John McCarthy
01200	
01300		Visionaries have often proposed that homes be  equipped  with
01400	information  terminals each consisting of a typewriter keyboard and a
01500	screen capable of displaying one or more pages of print and pictures.
01600	The  terminal  is  to  be  connected  by  the  telephone  system to a
01700	time-shared computer which in turn has access to files containing all
01800	books,  magazines,  newspapers,  catalogs,  airline  schedules,  much
01900	additional  public  information  not  now  kept,  and  various  files
02000	personal to the user.
02100	
02200		Through  the  terminal  the  user  can get any information he
02300	wants,  can  buy  and  sell,  could  communicate  with  persons   and
02400	institutions,  and process information in other useful ways.   Such a
02500	system has never come about because it costs too much, but with  each
02600	advance  in  technology,  it becomes more feasible.  I think that the
02700	technology of computers,  time-sharing,  terminals,  and  application
02800	programming  has  advanced to the point where realistic estimates are
02900	possible of the remaining advances necessary to  make  home  consoles
03000	feasible  and useful.  In this paper, I shall discuss the uses of the
03100	home terminal, some potential beneficial effects on society, estimate
03200	how  far  we are from a system people will pay for, and advocate some
03300	pilot projects, some  standardization  efforts,  and  some  laws  and
03400	regulations to prevent monopoly and secure adequate competition.
03500	
03600		We  can  start  with ordinary reading.  To get a newspaper or
03700	book, I type its name or number and the first page appears.  The most
03800	obvious benefits are:
03900	
04000		1. I can get any document instantly.
04100	
04200		2.  My  house  isn't  full  of  paper to be sorted and put on
04300	shelves and dusted or put in the trash.  Trees aren't cut  down,  and
04400	air pollution doesn't result from burning the stuff.
04500	
04600	Some immediately apparent disadvantages are:
04700	
04800		1. The expense.  I'll deal with this later.
04900	
05000		2. I can't read in bed.  The book size portable terminal will
05100	come later.  A household may require several terminals or perhaps  we
05200	may  have  to  compromise  with  sin and provide a hard copy terminal
05300	after all.
05400	
05500		There are two other immediate negative reactions:
05600	
05700		1.   The average citizen is a TV fan and doesn't read anyway.
05800	In the first place, our system doesn't need so many subscribers to be
05900	economical.   Secondly, after I have  described  all  the  bells  and
06000	whistles,  you will see that even the TV fan will be tempted, and you
06100	- oh socially conscious reader - may even want  to  coerce  him  into
06200	buying one or coerce the government into giving him one for free.
06300	
06400		2. How can you think of one more convenience and comfort when
06500	the world will come to an end in ten years unless menaces A, B, and C
06600	are  dealt  with  immediately.  In the first place, I don't think the
06700	world is about to come to an end or even that it  is  getting  worse,
06800	and we Americans like new gadgets.  In the second place, you will see
06900	that the new information system will make the public more  responsive
07000	to  the  careful  reasoning  of  you good guys and more immune to the
07100	blatant propaganda of those bad guys.
07200	
07300		In order to see the effects of the  new  information  system,
07400	suppose  that all book and newspaper information were so distributed.
07500	What changes would occur?
07600	
07700		At present, a newspaper or a book is a package produced by  a
07800	large  organization.       In our new system, the physical production
07900	disappears, allowing a much smaller organization to put out the  same
08000	packages  of  text  and pictures.  Moreover, the user does not face a
08100	one shot decision to buy Life or Look.  He will be able to  read  the
08200	"cover"  or  table of contents of each, read such items as strike his
08300	fancy, and the system will bill him  for  what  he  reads  from  each
08400	source.   In fact, since the cost of keeping a file of information in
08500	the computer and making it publicly available will be small,  even  a
08600	high  school  student  could  compete with the New Yorker if he could
08700	write well enough and if word  of  mouth  and  mention  by  reviewers
08800	brought him to public attention.      What, then, is a publication in
08900	the new information system?
09000	
09100		A publication is an organization that  puts  out  a  list  of
09200	material  it  has edited and recommends to its readers.  It helps its
09300	authors produce material that it thinks will suit the readers, and it
09400	has a financial arrangement with them about splitting the proceeds.
09500	
09600		There  can  be  a  wide  variety of publications of different
09700	standards of writing and editing and different budgets  for  carrying
09800	out  these  activities.  However, they will all be equally accessible
09900	to all readers, and the only justification for an expensive editorial
10000	organization will be that it can produce a more popular package.  The
10100	price of reading a package can be set by the publishers.
10200	
10300		A reader may feel that he  needs  help  in  finding  his  way
10400	through  the totality of literature available to him.  Various people
10500	will be eager to make a living by providing it.      A  bookstore  or
10600	library  is  a  program  that  when  called  shows  the  "covers"  of
10700	publications.    Reviewers will produce lists for him and make  money
10800	when  he  reads  their  lists  or  by  kickbacks from the publishers.
10900	"Reading advisers" under some catchier name will  offer  to  generate
11000	lists just for him according to a profile of his interests.
11100	
11200		Advertising  in  the sense of something that can force itself
11300	on the attention of a reader will disappear because it  will  be  too
11400	easy  to  read  via  a program that screens out undesirable material.
11500	However, people will still want to know what is  for  sale  and  will
11600	still  want  to  see the seller's story about why they should buy it.
11700	Probably, Life will still be able to get money from advertisers; many
11800	people  will still want to know what is advertised in Life, but those
11900	who don't want to know will be able to avoid it automatically.
12000	
12100		Another effect is the possibility of  frequent  revisions  of
12200	articles  and  books.    An author can take into account new facts or
12300	other  people's  criticisms,  and  the  revision  will  take   effect
12400	immediately.      This  raises  1984ish  possibilities, so it must be
12500	provided that old versions remain available.  Those who  suspect  the
12600	whole system will keep their own copies of favorite material in their
12700	private files, on microfilm, or even on paper.
12800	
12900		Public controversy can be carried out more expeditiously than
13000	at  present.  If I read something that seems controversial, I can ask
13100	the system if anyone has filed a reply.     This,  together  with  an
13200	author's  ability  to revise his original statement, will lead people
13300	to converge on considered positions more quickly than at present even
13400	if they do not come to actual agreement.
13500	
13600		Famous  authors  will not need publishers because their loyal
13700	readers will have the system find their stuff automatically.
13800	
13900		To summarize:      the new information  system  will  promote
14000	intellectual  competition by reducing the price of entry, will permit
14100	readers to be selective, and will allow authors  to  revise  material
14200	until  they  are satisfied that it withstands criticism as well as it
14300	ever will.  This should make intellectual life more interesting.
14400	
14500		The financial  aspect  of  writing  would  presumably  be  as
14600	follows:     a  piece of written material has a price for reading it.
14700	(This price may be zero for amateur  writing,  political  propaganda,
14800	advertising,  and  for scientific journals).  The reader's account is
14900	debited  and  the  account  to  which   the   material   belongs   is
15000	automatically credited.  The reader will have the system balk at what
15100	he considers overpriced material.
15200	
15300		The new information system will have  a  profound  effect  on
15400	buying  and  selling.      Sellers of movies, groceries, automobiles,
15500	plumbing services and cures for baldness will find it advantageous to
15600	list  their  wares  in  the  information system together with current
15700	prices and availability.    The user can place an order  through  the
15800	system as he can by telephone, but he can do much more:
15900	
16000		1.    He can call on someone's program to scan the sellers of
16100	sports cars and propose what it considers the best deal. This program
16200	might even negotiate with programs representing the sellers.
16300	
16400		2.    He  can  tell  the  system whether last year's cure for
16500	baldness worked and a get a summary of  the  opinions  of  those  who
16600	bothered  to record their opinions of the cure he contemplates trying
16700	now.
16800	
16900		3.     He can  make  an  airplane  or  hotel  reservation  by
17000	interacting  with  a program the airline or hotel reservation company
17100	has written to tell him what is available. He  need  not  suffer  the
17200	delays  you  now get when you call an airline or travel agent at peak
17300	hours.
17400	
17500		4. Individual design and construction services can be offered
17600	through the system although this requires the development of computer
17700	controlled manufacturing techniques for various types of article. The
17800	idea  is  that  automated  design  programs  can  produce designs for
17900	articles meeting individual specifications.  Either by himself or  in
18000	consultation  with  an  expert, an individual would use the system to
18100	produce a design and display how it would look and  possibly  how  it
18200	would  perform.    Candidates for individual design include clothing,
18300	furniture, boats, electronic equipment, houses, and even cars.    The
18400	system  would  then  produce the instructions for controlling machine
18500	tools, fabric cutters, and also printed  instructions  for  the  hand
18600	parts  of  the  operation.  In general, it should be possible to make
18700	single objects  at  little  more  cost  than  present  mass  produced
18800	objects.     In some cases, there would even be savings, because mass
18900	production  requires  estimates  of  demand  that  are  often   wrong
19000	resulting  in  inventories that are expensive to sell or even have to
19100	be sold at a loss; the cost of this is made up by a general  increase
19200	in prices.
19300	
19400		There  are  many  more  useful  services  that can be offered
19500	through the new information system and again the system is  conducive
19600	to  competition.     Writing and storing a program and announcing its
19700	availability can be a very low capital operation, and the system  can
19800	collect whatever price has been set for its use.
19900	
20000		We could go on listing services that would come to be offered
20100	in a fully developed system, but now we shall list some  services  to
20200	smaller  groups  of  users that are cheaper to provide and which will
20300	help get the system started.
20400	
20500		1. Calculation  and  facilities  for  writing,  running,  and
20600	debugging  computer  programs.      This doesn't interest the general
20700	public much, but it is the present bread  and  butter  of  the  time-
20800	sharing  service  bureaus  that  will  grow  into the new information
20900	system.  At present, these service bureaus offer very convenient  way
21000	of  doing  small  scientific and engineering calculations, but do not
21100	offer reasonable prices for big computations, and are only  beginning
21200	to offer useful services to business firms.
21300	
21400		2.     Editing.      Anyone who writes (writers, journalists,
21500	scientists, advertising men, engineers  and  students)  will  benefit
21600	from  using  an editor program.  It allows easy revision, can be made
21700	to  check  spelling,  grammar,  and  punctuation,  and  will  produce
21800	justified or other forms of elegant output and also indexes.
21900	
22000		3.  Filing.  Keeping personal files in the computer has great
22100	advantages once documents  can  be  entered  without  retyping  them,
22200	either because they have been prepared in a computer readable form or
22300	because a suitable page reader is available.        Namely,  one  can
22400	retrieve  any  document  on  the basis of its characteristics without
22500	having taken the trouble to file it properly in the first place.
22600	
22700		4. Education.  Computer aided instruction (CAI) has  advanced
22800	to  the point that a number of courses or aids to traditional courses
22900	have been developed and have been shown to be useful.       The  main
23000	obstacle   to  the  widespread  use  of  CAI  is  economic,  but  new
23100	developments  in  display  technology  and  communications   give   a
23200	reasonable  probability of cost-effective systems within this decade.
23300	There is no special problem in having these systems available in  the
23400	home  as  well  as  at  school.  This would be aided by standardizing
23500	course writing languages.      Again,  we  should  try  to  stimulate
23600	competition  by  encouraging  the  offering  of courses in particular
23700	subjects independent of the schools.
23800	
23900		The development of  such  a  system  is  probably  inevitable
24000	(unless  it  is  forbidden  by law) as soon as costs come down to the
24100	point where it is profitable  for  time-sharing  service  bureaus  to
24200	offer  services  to  individuals.   However,  favorable policies will
24300	bring this about sooner and will make the effects better.
24400	
24500		The main danger to be avoided is the creation of services  of
24600	limited  scope that through some avoidable feature cannot be expanded
24700	to provide the services mentioned here and  many  more.       Another
24800	problem  is  to  avoid monopolies; the intrinsic nature of the system
24900	permits any person who can write computer programs  to  compete  with
25000	large  organizations  in inventing and offering imaginative services,
25100	but one can worry that the system might develop commercially in  some
25200	way  that  would  prevent that.  In general, we should try to develop
25300	information services in such a way as will enhance the  individuality
25400	of its users.
25500	
25600		Between  us  and  the home information system lie a number of
25700	problems, some in developing suitable low  cost  terminals,  some  in
25800	programming  technology  of  time-sharing,  some in the economics and
25900	politics of communication systems, and some in the  attitude  of  the
26000	public  and government towards innovation.  In the following sections
26100	we shall discuss these problems.
26200	
26300	
26400	How we get there from here.
26500	
26600	1. Consoles.
26700	
26800		The   quality  and  price  of  display  consoles  is  rapidly
26900	improving. At present, one can add a display console with keyboard to
27000	our  laboratory system for about $700, but to add another port on the
27100	system so that the number of consoles active at one time is increased
27200	by  one  costs about $2500.  A reasonable display console that can be
27300	located at the end of a telephone line now costs about $10,000. These
27400	consoles  are  adequate  for  any  of  the  services mentioned in the
27500	previous  section,  although  for  reading  purposes,  it  would   be
27600	desirable to be able to display more than 35 typed lines at a time.
27700	
27800		In  my opinion, the cost of an adequate display terminal that
27900	can be located at the end of a telephone line will be in the $500  to
28000	$1000  range  by  1975  even  without  a  market  of  the size of the
28100	potential home terminal  market.     The  business,  engineering  and
28200	science,  and  government  markets  will  be  large  enough and price
28300	sensitive enough to bring this about.
28400	
28500		Another contender as a terminal is the plasma panel, but  the
28600	above  estimates  are based on CRT terminals with a mini-computer and
28700	an integrated circuit memory.
28800	
28900	
29000	2. Communications.
29100	
29200		In   the   United   States,   the   facilities   for  digital
29300	communications are growing rapidly but in  a  rather  disorderly  way
29400	because   of  the  multiplicity  of  requirements  of  the  different
29500	applications.   Some applications such as credit verification require
29600	very low cost short communications with turn around times of seconds.
29700	Others require very low cost per bit but can stand delays of  minutes
29800	and  hence  are  candidates  for  low  performance  store and forward
29900	systems.   The terminal systems require  long  holding  times,  short
30000	response  times, and much higher transmission rates from the computer
30100	to the user than in the other direction.
30200	
30300		For  the  purposes  of  the  home  terminal,  the  speeds  of
30400	transmission  over  present  unconditioned voice grade circuits are a
30500	bit too low for such applications as reading.  1200 bits  per  second
30600	would  take  20 seconds to transmit a typed page and about four times
30700	that for a page of a dictionary.  Eight times this rate  is  obtained
30800	over  conditioned  voice  grade  lines,  and  this  might  be  barely
30900	adequate.   Perhaps a better bet is the transmission facility planned
31000	for the Picturephone service now being introduced experimentally, but
31100	the  cost  of  this  service  for  long  holding  times  is  not  yet
31200	determined.  The most economical system might be a specially designed
31300	store and forward system configured to  give  fast  turn  around  for
31400	short messages.
31500	
31600		Whether  such  a  service  will  be made available depends on
31700	political as well as technical factors.  For example, if on the basis
31800	of  present  plans,  the  digital  communication market is divided by
31900	regulatory action among AT&T and its potential competitors, it  might
32000	turn  out that no-one is obliged or even allowed to offer the service
32100	required for home terminals at a reasonable cost.
32200	
32300	
32400	3. Computer technology.
32500	
32600		At  present,  computer  technology  can  offer  the  services
32700	required for  the  home  terminal  at  a  reasonable  cost,  provided
32800	computer  configurations  are  optimized  for  the  purpose, provided
32900	reasonable load factors can  be  obtained,  and  provided  there  are
33000	reasonable  economies  of  scale.    Unfortunately, IBM computers are
33100	organized in such a way that time sharing is very  expensive  because
33200	of  their interrupt structure, their expensive terminal multiplexors,
33300	and  their  dedication  to  the  archaic  half   duplex   method   of
33400	communication.   The  other major computer manufacturers such as CDC,
33500	General Electric, and Univac are not in much better shape since  they
33600	offer  for  time  sharing,  machines  that  were  optimized for other
33700	purposes.   Smaller companies like  DEC  are  in  a  somewhat  better
33800	position.    However,  none  of these difficulties are permanent, and
33900	better organized computers  may  be  expected  once  the  factors  in
34000	computer  design  that make for good cost-performance in time sharing
34100	become clearer to the manufacturers.
34200	
34300		The present magnetic disk storage units are a bit marginal in
34400	cost  effectiveness for use with home terminals.  Thus storage on the
34500	new IBM 3330 disk would cost a user about $.03 per month to  store  a
34600	typewritten page making storage of extensive personal files expensive
34700	and private copies of books  at  $5  to$10  per  month  prohibitively
34800	expensive.    This would not be too expensive for national libraries,
34900	but it would be economically very difficult to get enough readers  to
35000	support  the  storage  of  books  on  magnetic disk files in the near
35100	future.
35200	
35300		Fortunately, much larger files are becoming available.    The
35400	laser  file  made by Precision Instruments Inc. is claimed to store a
35500	trillion bits and costs $1,000,000.  This comes to about $4 per  book
35600	which  is reasonable even for single copies.  Mass production of such
35700	files will reduce the cost even further.
35800	
35900	
36000	4. Computer programming.
36100	
36200		The  basic  technology  of writing time sharing technology is
36300	reasonably well developed in that cost effective  systems  have  been
36400	written, but there is still a lot of chasing of will-o'-the-wisps and
36500	quite  bad  time-sharing  systems  are  often  produced  by otherwise
36600	competent firms.     Before the programming  required  to  offer  the
36700	services   mentioned   in  the  first  part  of  this  paper  can  be
36800	accomplished some further advances need to be made including at least
36900	the following:
37000	
37100		1.  The interactive and file reference aspects of programming
37200	languages and time sharing systems need to be standardized so that an
37300	interactive system written in one system can be used in another  that
37400	uses  different hardware and a different time sharing system. Without
37500	this it will be very expensive for new user  services  to  get  large
37600	markets unless some particular time sharing system gets a monopoly.
37700	
37800		2.  A system needs to be developed for representing text in a
37900	computer that will include the full variety of alphabets, type  fonts
38000	and  character  sizes and also be adaptable to diagrams, drawings and
38100	photographs.  The consoles also have to be adapted to this variety of
38200	styles.  This is an ultimate requirement; much can be done with texts
38300	that are just regarded as sequences of latin letters.
38400	
38500		3.  The biggest task, however, is the application programming
38600	itself.
38700	
38800	
38900	5. Commercial organization.
39000	
39100		From a social point of view, one of the  attractive  features
39200	of the provision of time-sharing services is that it is not a natural
39300	monopoly.      Communication  is  cheap  enough  for  teletype  based
39400	time-sharing  so  that  with local multiplexors, time-sharing bureaus
39500	can compete all over the United States.  In principal, it  should  be
39600	possible  to have world wide competition.  The major force that might
39700	tend to reduce competition is the exclusive possession of proprietary
39800	programs  or  files.    Therefore,  it  is  desirable to separate the
39900	ownership of programs performing services from the ownership  of  the
40000	service  bureaus  themselves  and  to  encourage enough compatibility
40100	between different time-sharing systems so that the owner of a service
40200	program  could  provide  it  on  a  number  of machines.   It is also
40300	important that important files  be  accessible  and  modifiable  with
40400	suitable  protections by actions initiated on other machines than the
40500	one that maintains the file.
40600	
40700	
40800	6. Needs for research and development.
40900	
41000		The hardware required for home consoles will be too expensive
41100	for extensive systems for  probably  another  five  years.    In  the
41200	meantime,  research  and  development  should  be  undertaken  in the
41300	following areas:
41400	
41500		1.  Standardization of the interfaces of time-sharing systems
41600	and their languages.
41700	
41800		2.   Experimentation  with services.   At present, it is very
41900	difficult to get support for development of generally useful services
42000	unless  either  it  can  be  claimed  that  disaster will result from
42100	failure to support the activity or that the  supporting  organization
42200	will itself make a profit.  This political fact is one of the reasons
42300	for the concentration on military technology in the recent past.
42400	
42500		3. Research aimed at devising ways of co-ordinating the great
42600	variety  of  time-sharing  services  into  a  mutually  communicating
42700	network.    Neither sufficient understanding nor sufficient political
42800	or  commercial  force  is  available  to  cause  the  development  of
42900	time-sharing  services  to  proceed  according  to  a  unified  plan.
43000	Nevertheless,  computers  are  flexible  enough  so  that  originally
43100	incompatible systems can be made to communicate and use each  other's
43200	services.      Experiments   with  the  ARPA  network  that  provides
43300	communication between U.S.  Government sponsored  research  computers
43400	will provide useful information.
43500	
43600	
43700	7. Comments on the conference.
43800	
43900		In general, the conference showed a  poor  situation  in  the
44000	scientific  and  technological  community and also the public affairs
44100	community regarding technology and the human future.   There  were  a
44200	few  technically competent but rather narrow surveys of the state and
44300	prospects of particular tool areas of technology.    There  was  much
44400	random doom-saying and denunciation of currently fashionable whipping
44500	boys.   There was a fair amount of opinion that certain things should
44600	not  be  done.     There  was  an  almost  total  lack of imaginative
44700	discussion of the opportunities technology offers us to improve human
44800	life.  This  lack  was  especially  notable  in those individuals and
44900	organizations that are supposed to be professionally  concerned  with
45000	the matter.
45100	
45200		This essay represents a small effort to redress the balance.