A SIMPLE GUIDE TO HOMECOMPUTERSBy Steve Ditlea

To my parentsfor making science accessible, and to Mr. Wizard for keeping it simple.

Book Design by Jos. Trautwein

Copyright ® 1979 by Steve DitleaAll rights reserved. No part of this work may be reproduced or trans­mitted in any form or by any means, electronic or mechanical, includ­ing photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher.Published by A & W Publishers, Inc.95 Madison Avenue New York, New York 10016Library of Congress Catalog Card Number: 78-70685ISBN: 0-89104-108-7 (HC)

0-89104-109-5 (PB)Printed in the United States of America

CONTENTS

Introduction 11

PART I: Home Computer Fundamentals 17

1 The Home Computer Revolution 182 Welcome to Computer Nation 313 Anatomy of a Home Computer 434 Binary Thoughts 625 Birth of the Microprocessor 74

PART II: Choosing a Home Computer 89

6 Home Computer Characteristics 907 Programmable Video Games 1068 Compact Home Computers 1179 Keyboard Mainframes 128

10 Component Systems 142

PART III: Using Your Home Computer 15711 Hardware, Software, and You 15812 Basically Basic 168

EPILOGUE 186

Glossary 199Binary Conversion Table 211Index 215

PROGRAMMABLE VIDEO GAMES

■ The video game was originally an expensive toy that could only perform a single function. Who could foresee that the coin-operated electronic ping-pong game featured in bars and college lounges would prepare the way for versatile computers in the home?

Introduced in 1972, the first video games for home use car­ried price tags with three figures and were “dedicated” de­vices, that is, they performed only one built-in function for the user: Ping-pong. As more and more people bought these video games, prices dropped by half and by half again, and the idea of connecting something to the home TV set to permit interaction with the picture tube became commonplace for many Ameri­cans.

In 1977 over four million home video games were sold in the United States. In 1978 that number nearly doubled. As con­sumers became more sophisticated, manufacturers introduced

multi-purpose video games (combining ping-pong, tennis, handball, etc.) which were still dedicated, performing only those functions built into them.

Even with these added features, the more demanding con­sumers tended to get bored when the novelty wore off their video games. They could only be satisfied with a programmable game. To satisfy this growing market, units were developed that allowed new games to be fed onto the video screen simply by inserting a new program cartridge into a handy slot. Within a year of their introduction, Americans had purchased over one million programmable game units— the strongest response coming from men between the ages of 35 to 45 with sons, and younger adults with no children.

A programmable video game (the name used for the entire unit) is built around a microprocessor that can be programmed with a cartridge-full of instructions stored in a ROM chip or on a cassette tape. Take input in the form of a joy stick or other con­trol device, display the output on your home TV screen, and you have the elementary workings of a home computer.

When manufacturers called their units “computer video games,” some veteran computer hobbyists were outraged. These hard-core “hackers,” pioneers in the use of computers at home, argued that no video game could attain the versatility and calculating power of a genuine microcomputer system.

Video game makers were soon using 8-bit microprocessors in their programmable units. To create a true home computer sys­tem, all they had to add was a means for entering letters and numbers as input, and such peripheral devices as the individ­ual user might require.

The first expandable programmable TV games are now avail­able to the public at base prices ranging from $179 to $500.

Add-on components can run into hundreds of dollars more, but without them most of these models are just glorified kids’ games.

It’s their simplicity that makes expandable video games so attractive to potential buyers. The initial investment is rela­tively small; the amount of pleasure that can be derived with­out knowing anything about programming seems well worth the cost.

Besides, the video game is easily mastered, and it can serve as an entertaining introduction to home computers. Users will find themselves programming a microprocessor without realiz­ing it at first. Then with programming no longer a foreign no­tion, millions of Americans will be able to pick up a program­ming language like BASIC and learn to create their own pro­grams.

So goes the manufacturers’ scenario. The aim, naturally, is to turn the home computer into a mass-market item; presumably, this will lead to further price reductions. For this reason the industry is concentrating sales in department and chain stores, rather than limiting distribution to specialty shops.

Like any of today’s personal computers, the popularity of expandable video games will depend on the availability of pre-programmed cartridges and cassettes. After the first pro­grammable video games were put on the market, it took over a year for additional software to be produced in sufficient quan­tities.

With the expandable games, individual manufacturers’ effort have been supplemented by the entrance ofG .R .T —the lead­ing maker of pre-recorded stereo cassettes—into the area of home computer software. Should these video games become runaway bestsellers, the price of a cartridge or cassette could tumble to that of a long-playing stereo record.

As with all the com puter models described in these pages, prices and specifications are subject to change. Until now, the unexpected has been the stock in trade of the consum er elec­tronics field; still any modifications or new models in the cur­rent generation of home computers will no doubt resem ble units like those described below.■ Odyssey2 Computer Video Game System— Magnavox was the pace-setter in video games with its Odyssey, the first model designed specifically for home use. Now the company has beaten rivals Atari and Fairchild to the market with an alpha­numeric programmable TV game, the Odyssey2.

Priced at just $179.95, the Odyssey2 represents an im portant price breakthrough. The base price model features an inexpen­sive full-size keyboard design: a flat plate that can be activated by touching any of the 49 characters indicated on its surface.

■ Bally Professional Arcade—Though new to the consumer electronics field, the Bally Manufacturing Corporation, in bus­iness since 1931, is the world’s largest manufacturer of coin­operated amusement games. Bally’s programmable video game, the Professional Arcade, was the first of the expandable home units to be advertised to the public.

Designed to sell for under $300, the Bally starter unit is structured around the same Zilog Z-80 microprocessor used in more expensive home computer systems. The Arcade module encloses 4K of RAM and 8K of ROM for a useful amount of internal memory.

Game-playing input is provided by four pistol-grip hand con­trols. Each has a trigger for shoot-out games as well as a knob that can be turned or swiveled like a joystick. Other input is entered with the help of a 24-key calculator-style key pad.

Built into the Arcade are three games: Gunfight, Checkmate

Data input is accomplished by electrical switches attached to the back of the plate, much like touch-operated elevator call buttons, thus eliminating failure-prone push type keys. The unit also comes with a pair of joysticks for playing arcade sports games.

The Odyssey2 is offered with a cartridge for three games: Speedway, Spin-Out, and a word game called Crypto-Logic. Among the optional programs available at $19.95 each are Football, Baseball, Las Vegas Blackjack, and a pair of learning games, Math-A-Magic and Echo.

For $24.95 there’s an Odyssey2 Computer Introduction car­tridge that teaches how to create and execute actual working computer programs. It also helps a user decide whether to ex­pand to a home computer in the future.

The Odyssey2 system has connectors for add-on units.

(a game of wits), and Scribbling (multi-color graphics), in addi­tion to a convenient calculator with five functions and ten memory locations. Another handy feature is a pause control which freezes action and allows it to be resumed without start­ing the program over again. The unit shuts itself off automati­cally when left unattended to prevent damage to the TV picture tube.

Bally offers a variety of software on Videocade cassettes (ac­tually ROM cartridges) at prices from $19.95 to $24.95. These cassettes include action games like Space Race, sports like Demolition Derby, educational programs like Bingo Math and Spell ‘N’ Score, and even an innovative Astrology cassette which will pinpoint the positions of stars and planets at any moment in the past, present, or future on a computer model of a planetarium.

The Bally BASIC program cassette turns the calculator key pad into the equivalent of an ASCII keyboard. It might seem a little slapdash to use a plastic key pad overlay and four different shift keys to express a full range of alphanumerics. This re­quires a lot of hunting and pecking on the user’s part. Yet, this Bally unit is intelligently designed so that you can feed in entire instruction words with the push of a single key.

The Bally BASIC program includes a limited, though well thought-out, set of instructions that allows simple user pro­grams for games, graphics, even music (with the help of a built-in 3-octave synthesizer). A clearly written and illustrated manual teaches elementary programming in a matter of min­utes. The BASIC Cassette also makes the Arcade the first home computer system to utilize a full color TV spectrum of 256 hues.

To turn the Professional Arcade into a fully operational home computer, Bally has made available an interface for tape cas-

sette mass storage and an ASCII-type keyboard with an ad­ditional 16 K of memory. Promised for the near future are a high-speed prin ter and a M ODEM telephone coupler.

One enterprising merchandiser has announced a Bally own­ers’ Dial-A-Bargain Ordering System. This program allows the Arcade to place orders for electronic gadgetry with the re­tailer’s com puter right over the phone.

■ Cybervision 2001 — By appearing in the Montgomery Ward Spring & Sum m er 1978 catalogue, the Cybervision 2001 be­came the first home com puter offered to middle America via mail order. Produced by the Broadrein Instrum ents Corpora­tion of Columbus, Ohio, the Cybervision has limited adaptabil­ity, bu t makes up for its shortcomings with unusual consumer- oriented software.

The Cybervision unit, which sells for $399, employs an RCA 1802 microprocessor along with 1K of operating instructions in

PROGRAMMABLE VIDEOGAM ES ■ 113

ROM and 4K of RAM memory. Input is entered with a pair of hand-held key pads of the touch activated type, bearing 40 dif­ferent characters.

Programs for this hybrid video game unit are stored on audio tape cassettes that can be played by a built-in tape deck. The cassette (or Cybersette) is used both for instructions to the com puter and for computer-controlled audio playback. This gives Cybervision 2001 the capability to entertain with music or special effects, and— using human voices— even to tell stories or provide instruction for educational programs.

Cybersettes retail for $10. Program titles are divided into a Home Series (Checkbook, Recipe File), Party Series (Trivia, Designer), Story Series (Three Little Pigs, E m peror’s New Clothes), Education Series (Math Grade 1, Language Arts Grade 1), and the Game series (Bandit, Bulldozer). Program­ming is quick, thanks to an entry rate faster than any standard

The Cybervision 2001 offers listen-and-learn audio cassettes. (Photo courtesy o f Broadrien Instruments)

cassette tape input. Tape to screen data transfer is also said to be faster than with any other home computer.

Still to come are several accessory units for the Cybervision 2001. These will make it possible to increase its capacity and to create original Cybersettes at home.■ VideoBrain— In 1978 the VideoBrain became the first home com puter system sold in departm ent stores. Advertised with the slogan “‘now you don’t have to leave your brains at the office, ” the $500 VideoBrain drew the greatest response for a new product in the history of Macy’s in New York and San Francisco.

The VideoBrain is manufactured in Silicon Valley by a divi­sion of Umtech, Inc. The brains behind the champagne of video games are Dr. Albert Yu and Dr. David Chung, co­founders of the VideoBrain Computer Company. Dr. Yu guided product research at Intel, while Dr. Chung invented and man­aged the development of the Fairchild F8 microprocessor, one of the most widely used silicon brains.

The VideoBrain uses an F8 microprocessor coupled with 4K of ROM and IK of RAM. Plug-in cartridges can add as much as 12K of ROM memory. The system’s module has a keyboard with 36 push-type keys allowing the entry of 71 input symbols. Built-in VideoBrain features include a clock, alarm, and calen­dar activated by pressing a key. The computer unit also has connectors for up to four joysticks.

In creating program cartridges for the VideoBrain, its mak­ers have emphasized financial and educational applications. Among the more imaginative offerings priced from $29.95 to $70.00 are Money Manager (an aid in keeping track of house­hold and personal finances), Lemonade Stand (a business simu­lation that illustrates fundamentals of management and economics), and Old Regime (a Stanford History professor’s simulation of pre-revolutionary France).

For users who want to create their own programs, there’s a cartridge that provides STRUCTURE BASIC, a version of BASIC that facilitates financial programming. Of course, games haven’t been neglected: VideoBrain offers Checkers, with the computer programmed for any of four skill levels, while the Gladiator cartridge provides 384 varieties of man- to-man combat.

Among the VideoBrain’s options is the Expander 1 ($150), which acts as an interface for a pair of cassette recorders and a

hard copy printer. The Expander 2 ($300), a telephone MODEM, can be used in conjunction with a Timeshare pro­gram cartridge to communicate with a large time-sharing com­puter.

Future expansion units will include a light pen, special key­boards, a voice response interface, and home controllers. Ac­cording to VideoBrain Computer Company’s rosy vision of the future: “VideoBrain will even be able to monitor and record your telephone messages, start up the morning coffee, and regulate your home’s temperature for maximum efficiency.’’

Though the cost of add-on’s may ultimately make expandable video games as expensive as their more sophisticated compet­itors in the home computer field, these starter units represent a good value for the average consumer. Programmable video games can provide users with the simplest of computer func­tions in the form of games, as well as educational and financial programs, displayed in dazzling color on home TV screens with push-button simplicity.

But what if you’d rather not have to switch off your favorite television show so Junior can use the computer? Or perhaps the thought of learning BASIC and creating your own powerful programs turns you on. Then an expandable video game just won’t be enough for you.

Clearly, there is a place for fully equipped home computer systems priced within reach of consumers. Indeed, compact computer systems selling for under $800 have proven to be the most popular units on the market.

INDEX

Abacus, 33Access (newsletter), 140 Accumulator, 53 Adding binary numbers, 65 Advanced Research and

Development Agency, 40 Aiken, Howard, 37—38 ALGOL (ALGOrithmic

Language), 172 Alphanumerics, 46 Analog to digital interface, 40 “Analytical Engine,” 34-37 Apple Computer Inc., 27, 135 Apple II, 135-138 Arabic numerals, 33-34 Arithmetic, binary, 63-67 Arithmetic/logic unit (ALU),

52-53Artificial intelligence, 197 ASCII keyboard, 91, 92, 94 Assembly language, 92

Babbage, Charles, 34-37 Bally Professional Arcade,

110-112 BASIC (Beginners’ All-Purpose

Symbolic Instruction Code) language, 92-93, 99, 108, 130, 134, 139, 160, 164, 167, 174, 190-191; writing your own program, 168-185

Bell Telephone Laboratories, 74, 77

Biele, John, 22 Binary adder, 70 Binary digit (or “bit”), 47 Binary switching, 37 Binary system, 47, 62-73;

arithmetic, 63-67; logic, 67-73

Bipolar transistor, 77 Bit. See Binary digit Bits per second, 102

216 ■ INDEX

Boole, George, 37, 67-68 Bootstrap, 100 BREAK, ESCAPE, or

CONTROL key, 164 Bus, 55BYTE (magazine), 166 Bytes, 49Bytes per second, 102

Capacitors, 94 Central processing,

characteristics of, 94-98 Central processing unit (CPU),

48Challenger III, 131 Challenger IIP, 129-131 Character reader, 93 Charge coupled devices

(CCD), 189 CLEAR or RESET key, 164 Clock circuit, 51-52 COBOL (COmmon Business

Oriented Language), 172 Combinational logic, 69 Commodore Business

Machines, 27, 123 Compact home computers,

117-127; PET 2001, 122-127; TRS-80, 118-122

Comparator, 72 Component systems, 142-155 Compucolor Corporation, 131 Compucolor II, 131-133 Conditional branching, 182 Conductors, 76 Contact (newsletter), 136 Control unit, 51

Cost effectiveness, 41-42 Cray Research, Inc., 30 Creative Computing

(magazine), 166 Cromemco, Inc., 146-147 CRT (cathode ray tube), 58-59 Cursor control, 104 Cybervision 2001, 112-114

Daisywheel, 104 Data, 48 Debugging, 172 Decoder circuit, 72 Dedicated devices, 86-87 Designs (graphics), 58 Digital Equipment

Corporation (DEC), 40 Digital Group System,

147-148 Direct access capability, 103 Disk drive, 56Disk operating system (DOS),

103Division, binary, 67 Doping process, 76 Dr. Dobb’s Journal of

Computer Calisthenics and Orthodontia, 166

Dual in-line packages (DIP), 94-95

Eckert, J. Presper, 38 Electrons, 75-76 Engstrom, Lynda, 22-23 ENIAC (Electronical

Numerical Integrator and Computer), 18, 27, 38-39

INDEX ■ 217

Enlightenment, 34 Erasable programmable

read-only memory (EPROM), 100, 101

Execute command, 51 Exponent, 178 External clock circuit, 51-52

Fainman, Kurt, 22 Fairchild Camera and

Instrument Corporation, 26 Fairchild F8 microprocessor, 98 Fairchild Semi-Conductor, 26 Fetch, 51Fiedler, David, 22, 169 Field-effect transistor, 79, 80 Flip-flop circuit, 72 Floppy disks, 103 Flowchart, 170 FORTRAN (FORmula

TRANslation), 172

General Electronic Company, 30

Hardware, 50, 51; using, 158-167

Heath H8, 148-149 Heathkit Hll, 188 Hexadecimal system, 91 Heyser, Dick, 165 Holes (in atoms), 76 Hollerith, Hans, 37 Home computers: anatomy of,

43-61; binary system, 47, 62-73; choosing, 89—155; compact types, 117-127; component systems,

142-155; fundamentals of,17-87; future and, 186-198; glossary, 199-209; introduction to, 11-16; keyboard mainframes, 128-141; number of (by 1982), 186; revolution in,18-30; in U.S., 31—42; using, 157-185; writing your own program ,168-185

HORIZON, 151-152

IBM 360 computer system, 40 Imsai Company, 27 IM SA I8080, 149-151 Input, 44-47; characteristics

of, 90-94 Input/output (I/O) devices, 57 Instruction register, 53 Instructions, 48 Instruction set, 49 Insulators, 76 Integrated circuits (IC), 77 Integrated Electronic (Intel),

27, 80-81 Intel 8008, 81 Intel 8080, 96-97 Intel 8085, 96-97 Interface, 46Interface (newsletter), 166 Interface Age (magazine), 166 Interface circuit, 46 Internal Revenue Service, 32 International Business

Machines (IBM), 30, 37-38, 40

Inverting binary digits, 65-66

218 ■ INDEX

Jobs, Steven, 135 Joystick, 93

Kansas City or Byte (30 bytes/second), 102

Kauffman, H. R ., 133-134 Kemeny, John, 174 Keyboard interface, 92 Keyboard mainframes,

128-141 Kilobaud (magazine), 166 Kilobyte (K), 98 Kodak Company, 86 Komfeld, Lewis, 119 Kurtz, Thomas, 174

Large scale integration (LSI),79-80

Latch, 72Leibnitz, Gottfried Wilhelm,

34Letters and numbers

(alphanumerics), 57-58 Level-I BASIC, 121, 122 Level-II BASIC, 122 Line number, 179 Line printers, 59, 104 Liquid crystal display (LCD),

190LISP (LISt Processing)

language, 172 LOAD and RUN, 162 Logic, binary, 67-73

Machine language, 92 Magnetic bubble, 189 Magnetic disk, 56

Mainframe, 55 Mantissa, 178 MARK I, 37-39 Mass storage devices, 56 Math I, 121Matrix arrangement, 104 Mauchly, John, 38 Medium scale integration

(MSI), 77 Memory, 53-57; characteristics

of, 98-103 Memory chips, 55 Microprocessing unit (MPU),

48Microprocessors, 74-87; chips,

82-84; dedicated, 86-87; silicon basis, 83-84

Mini-floppies, 103 Mintz, Ezra, 133 MITS (30 bytes/second), 102 MITS Altair 8800, 27, 29, 81, 96 MITS Altair 8800b, 143-144 MITS, Inc., 27, 29 MITS S-100 bus, 96 MODEM IIA, 137 M odulator-demodulator

(MODEM), 60 Monitor program, 172 MOS 6502 microprocessor,

124MOS Technology, 98 Motorola 6800, 97-98 Motorola S-100 bus, 98 Motorola SS-50 bus, 98 Multiplication, binary, 66 Music synthesizer, 60

INDEX ■ 219

National Aeronautics and Space Administration (NASA), 25

National Security Agency, 32 Negative charge, 76 Neumann, John von, 39 NPN (or pnp) transistor, 76 N-type semiconductor, 76

Octal numbering system, 91 Odyssey Computer Video

Game System, 109-110 Ohio Scientific Instruments,

129 On or off, 47 Optical scanner, 46 Output, characteristics of,

103-105

Panasonic Company, 30 Paper tape punch, 60 Paper tape reader, 60 Parallel port, 94 Pascal, Blaise, 34 PDP-11 small computer, 40 PeCos One, 144-146 Peripheral devices, 46 Permanent (hard copy) form, 59 Personal Computing

(magazine), 166 PET BASIC, 124 PET 2001, 122-127 Poly 88, 21-22, 152-154 Popular Electronics (magazine),

27, 166 Port, input, 93 Power supply, 94 Printed circuit (PC) boards, 94

Processing, 47-53 Processor Technology

computer, 27 Program counter, 53 Programmable read-only

memory (PROM), 100 Programming language, 92 P-type semiconductor, 76

Radio Electronics (magazine), 166

Radio Shack TRS-80, 97 Random-access memory

(RAM), 100, 101, 164 RCA Company, 30 Read-only memory (ROM),

99-100, 189 Read-write head, 103 Register latch, 72-73 Relays, outlet, 61 Remington Rand, 27 Resistors, 94 RETURN key, 161, 162 RF modulator, 103 RUN (and RETURN), 164

Scientific notation, 178 Scrolling, 104 Semiconductors, 76 Sensor, electronic, 46 Sequential devices, 102 Serial ports, 93-94 Shannon, Claude, 68 Shockley Transistor Company,

26Shockley, William, 26

220 ■ INDEX

16K RAM Memory Kit, 121, 122

Small scale integration (SSI), 77 SNOBOL language, 172 Software, 50; using, 158-167 Solomon, Leslie, 138 Sol-20, 138-141 Sony Company, 30 Sorcerer, 133-135 Southern California Computer

Society, 166 Specifications (or specs) ,*90-91 Speisel, Dr. Sydney, 23 STRUCTURE BASIC, 115 Subroutines, 185 Subtraction, binary numbers,

65-66 Synchronous motors, 61

Tape cassette memory, 56 Tarbell (187 or 540

bytes/second), 102 TDL (120 bytes/second), 102 Teletype (TTY), 60 Texas Instruments, 30, 79,

80-81, 189 Tiny BASIC, 174 Transistors, 74-75, 94 Transistor transistor logic

(TTL), 78 TRS-80home computer, 20,21,

118-122, 160

Truth table, 68 Two’s complement, 65

UMTECH computer, 27 UMTECH VideoBrain, 19, 20 Underwriters’ Laboratories,

120Universal Product Code

(UPC), 93 U. S. Department of Defense,

40

Vector 1, 154-155 Veit, Stanley, 165, 197 VideoBrain, 114-115 Video display monitor, 57-58 Video games, 106-116 Video interface, 58 VMOS (V-groove metal oxide

semiconductor), 188 Vocal interface, 46, 93 Vocal synthesizer, 60

Wozniak, Stephen, 135

Xerox Corporation, 86 XITAN, 155

Zero, concept of, 33-34Zilog Z-80 chip, 97Z-2 (Cromemco, Inc.), 146-147