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The Altair 8800 is a
microcomputer A microcomputer is a small, relatively inexpensive computer with a microprocessor as its central processing unit (CPU). It includes a microprocessor, Computer memory, memory and minimal input/output (I/O) circuitry mounted on a single printed ci ...
designed in 1974 by MITS and based on the
Intel 8080 The Intel 8080 (''"eighty-eighty"'') is the second 8-bit microprocessor designed and manufactured by Intel. It first appeared in April 1974 and is an extended and enhanced variant of the earlier Intel 8008, 8008 design, although without binary ...
CPU A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuit File:PExdcr01CJC.jpg, 200px, A circuit built on a printed circuit board (PCB). An electronic circuit is composed of ...

CPU
. Interest grew quickly after it was featured on the cover of the January 1975 issue of Popular Electronics and was sold by mail order through advertisements there, in ''
Radio-Electronics ''Radio-Electronics'' was an American electronics magazine that was published under various titles from 1929 to 2003. Hugo Gernsback Image:Radio News Nov 1928 Cover.jpg, 200px, right , Gernsback watching a television broadcast by his station WRN ...
'', and in other hobbyist magazines. The Altair is widely recognized as the spark that ignited the
microcomputer revolution The history of the personal computer as a mass-market consumer electronic device began with the microcomputer revolution of the 1970s. A personal computer is one intended for interactive individual use, as opposed to a mainframe computer where t ...
as the first commercially successful personal computer. The
computer bus In computer architecture In computer engineering, computer architecture is a set of rules and methods that describe the functionality, organization, and implementation of computer A computer is a machine that can be programmed to carry ...
designed for the Altair was to become a ''de facto'' standard in the form of the
S-100 bus The S-100 bus or Altair bus, IEEE 696-1983 ''(withdrawn)'', is an early computer bus In computer architecture In computer engineering, computer architecture is a set of rules and methods that describe the functionality, organization, and ...
, and the first programming language for the machine was
Microsoft Microsoft Corporation is an American multinational corporation, multinational technology company, technology corporation which produces Software, computer software, consumer electronics, personal computers, and related services. Its best-know ...

Microsoft
's founding product,
Altair BASIC Altair BASIC is a discontinued interpreter for the BASIC programming language BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of General-purpose programming language, general-purpose, high-level programming languages whos ...
. "This announcement ltair 8800ranks with IBM's announcement of the System/360 a decade earlier as one of the most significant in the history of computing."


History

While serving at the
Air Force
Air Force
Weapons Laboratory at
Kirtland Air Force Base Kirtland Air Force Base is a United States Air Force base located in the southeast quadrant of the Albuquerque, New Mexico, Albuquerque, New Mexico urban area, adjacent to the Albuquerque International Sunport. The base was named for the earl ...
, Ed Roberts and Forrest M. Mims III decided to use their electronics background to produce small kits for
model rocket A model rocket is a small rocket A rocket (from it, rocchetto, , bobbin/spool) is a spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite alt=, A full-size model of t ...

model rocket
hobbyists. In 1969, Roberts and Mims, along with Stan Cagle and Robert Zaller, founded
Micro Instrumentation and Telemetry Systems Micro Instrumentation and Telemetry Systems (MITS) was an American electronics company founded in Albuquerque, New Mexico Albuquerque ( , ), ; kee, Arawageeki; tow, Vakêêke; zun, Alo:ke:k'ya; apj, Gołgéeki'yé. abbreviated as ABQ, is th ...
(MITS) in Roberts' garage in
Albuquerque, New Mexico Albuquerque ( , ), ; kee, Arawageeki; tow, Vakêêke; zun, Alo:ke:k'ya; apj, Gołgéeki'yé. abbreviated as ABQ, is the most populous city in the U.S. state of New Mexico ) , population_demonym = New Mexican ( es, Neomexicano, Neomejica ...
, and started selling
radio Radio is the technology of signaling and telecommunication, communicating using radio waves. Radio waves are electromagnetic waves of frequency between 30 hertz (Hz) and 300 gigahertz (GHz). They are generated by an electronic device ...

radio
transmitter In electronics The field of electronics is a branch of physics and electrical engineering that deals with the emission, behaviour and effects of electrons The electron is a subatomic particle In physical sciences, subatomic particle ...
s and instruments for
model rocket A model rocket is a small rocket A rocket (from it, rocchetto, , bobbin/spool) is a spacecraft A spacecraft is a vehicle or machine designed to fly in outer space. A type of artificial satellite alt=, A full-size model of t ...

model rocket
s.


Calculators

The model rocket kits were a modest success and MITS wanted to try a kit that would appeal to more hobbyists. The November 1970 issue of ''Popular Electronics'' featured the Opticom, a kit from MITS that would send voice over an
LED An LED A light-emitting diode (LED) is a semiconductor A semiconductor material has an Electrical resistivity and conductivity, electrical conductivity value falling between that of a Electrical conductor, conductor, such as metallic ...
light beam. As Mims and Cagle were losing interest in the kit business, Roberts bought his partners out, then began developing a calculator kit. Electronic Arrays had just announced a set of six large scale integrated (LSI) circuit chips that would make a four-function calculator. The Electronic Arrays, Inc. calculator chipset that was used in the MITS 816 calculator. The
MITS 816
MITS 816
calculator kit used the chipset and was featured on the November 1971 cover of ''Popular Electronics''. This calculator kit sold for $175 ($275 assembled). Forrest Mims wrote the assembly manual for this kit and many others over the next several years. As payment for each manual he often accepted a copy of the kit. The calculator was successful and was followed by several improved models. The MITS 1440 calculator was featured in the July 1973 issues of ''Radio-Electronics''. It had a 14-digit display, memory, and
square root In mathematics Mathematics (from Greek: ) includes the study of such topics as numbers (arithmetic and number theory), formulas and related structures (algebra), shapes and spaces in which they are contained (geometry), and quantities ...

square root
function. The kit sold for $200 and the assembled version was $250. The cover story is for the MITS 1700 waveform generator. An ad for the MITS 1200, a $99 battery operated handheld calculator, is on page 15. MITS later developed a programmer unit that would connect to the 816 or 1440 calculator and allow programs of up to 256 steps.


Test equipment

In addition to calculators, MITS made a line of test equipment kits. These included an IC tester, a waveform generator, a digital voltmeter, and several other instruments. To keep up with the demand, MITS moved into a larger building at 6328 Linn NE in Albuquerque in 1973. They installed a
wave soldering Wave soldering is a bulk soldering Soldering (General American, AmE: , Received Pronunciation, BrE: ) is a process in which two or more items are joined together by melting and putting a filler metal (solder) into the joint, the filler met ...
machine and an assembly line at the new location. In 1972,
Texas Instruments Texas Instruments Incorporated (TI) is an America The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America North America is a ...
developed its own calculator chip and started selling complete calculators at less than half the price of other commercial models. MITS and many other companies were devastated by this, and Roberts struggled to reduce his quarter-million-dollar debt.


''Popular Electronics''

In January 1972, ''Popular Electronics'' merged with another
Ziff-Davis Ziff Davis, LLC, known as Ziff Davis (ZD), is an American digital media and internet company founded in 1927. Ziff Davis's brands and properties provide advertising, performance marketing, data services and licensing solutions to clients across ...
magazine, ''Electronics World''. The change in editorial staff upset many of their authors, and they started writing for a competing magazine, ''Radio-Electronics''. In 1972 and 1973, some of the best construction projects appeared in ''Radio-Electronics''. In 1974, Art Salsberg became editor of ''Popular Electronics''. It was Salsberg's goal to reclaim the lead in electronics projects. He was impressed with
Don Lancaster Donald E. Lancaster is an American author, inventor, and microcomputer A microcomputer is a small, relatively inexpensive computer with a microprocessor as its central processing unit (CPU). It includes a microprocessor, Computer memory, memo ...
's
TV Typewriter The TV Typewriter is a video terminal that could display two pages of 16 lines of 32 upper case characters on a standard television set A Sony Wega CRT television set A television set or television receiver, more commonly called the television ...
(''Radio Electronics'', September 1973) article and wanted computer projects for ''Popular Electronics''. Don Lancaster did an ASCII keyboard for ''Popular Electronics'' in April 1974. They were evaluating a computer trainer project by Jerry Ogden when the
Mark-8 The Mark-8 is a microcomputer A microcomputer is a small, relatively inexpensive computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern computers can perfo ...
8008
8008
-based computer by Jonathan Titus appeared on the July 1974 cover of ''Radio-Electronics''. The computer trainer was put on hold and the editors looked for a real computer system. (''Popular Electronics'' gave Jerry Ogden a column, ''Computer Bits'', starting in June 1975.) "The breakthrough in low-cost microprocessors occurred just before Christmas 1974, when the January issue of Popular Electronics reached readers … " One of the editors, Les Solomon, knew MITS was working on an Intel 8080 based computer project and thought Roberts could provide the project for the always popular January issue. The TV Typewriter and the Mark-8 computer projects were just a detailed set of plans and a set of bare printed circuit boards. The hobbyist faced the daunting task of acquiring all of the integrated circuits and other components. The editors of ''Popular Electronics'' wanted a complete kit in a professional-looking enclosure. Ed Roberts and his head engineer, Bill Yates, finished the first prototype in October 1974 and shipped it to ''Popular Electronics'' in New York via the
Railway Express Agency Early 20th century steamer trunk sticker The Railway Express Agency (REA), founded as the American Railway Express Agency and later renamed the American Railway Express Inc., was a national Package delivery, package delivery service that operate ...
. However, it never arrived due to a strike by the shipping company. Solomon already had a number of pictures of the machine and the article was based on them. Roberts got to work on building a replacement. The computer on the magazine cover is an empty box with just switches and LEDs on the front panel. The finished Altair computer had a completely different circuit board layout than the prototype shown in the magazine. The January 1975 issues appeared on newsstands a week before Christmas of 1974 and the kit was officially (if not yet practically) available for sale.


The name

The typical MITS product had a generic name like the " Model 1440 Calculator" or the " Model 1600 Digital Voltmeter". Ed Roberts was busy finishing the design and left the naming of the computer to the editors of ''Popular Electronics''. One explanation of the Altair name, which editor Les Solomon later told the audience at the first Altair Computer Convention (March 1976), is that the name was inspired by Les's 12-year-old daughter, Lauren. "She said why don't you call it Altair – that's where the Enterprise is going tonight.""Les Solomon entertained a curious audience with anecdotes about how it all began for MITS, The name for MITS' computer, for example, was inspired by his 12-year-old daughter. She said why don't you call it Altair -- that's where the ''Enterprise'' is going tonight." The ''
Star Trek ''Star Trek'' is an American science fiction media franchise created by Gene Roddenberry, which began with the Star Trek: The Original Series, eponymous 1960s series and quickly became a worldwide Popular culture, pop-culture Cultural influ ...
'' episode is probably "
Amok Time "Amok Time" is the second season premiere A premiere or première is the wikt:debut, debut (first public presentation) of a Play (theatre), play, film, dance, or musical composition. A work will often have many premières: a world première ...
", as this is the only one from ''The Original Series'' which takes the Enterprise crew to Altair (Six). Another explanation is that the Altair was originally going to be named the PE-8 (Popular Electronics 8-bit), but Les Solomon thought this name to be rather dull, so Les, Alexander Burawa (associate editor), and John McVeigh (technical editor) decided that: "It's a stellar event, so let's name it after a star." McVeigh suggested "
Altair Altair () designated α Aquilae ( to Alpha Aquilae, abbreviated Alpha Aql, α Aql), is the brightest in the of and the in the . It is currently in the —a nearby , an accumulation of gas and dust. Altair is an ...

Altair
", the twelfth brightest star in the sky. Salsberg states that the Altair was named by John McVeigh


Intel 8080

Ed Roberts had designed and manufactured programmable calculators and was familiar with the microprocessors available in 1974. He thought the
Intel 4004 The Intel 4004 is a 4-bit In , 4-bit s, or other units are those that are 4 s wide. Also, 4-bit and architectures are those that are based on s, or es of that size. es (and thus es) for 4-bit CPUs are generally much larger than 4-bi ...

Intel 4004
and
Intel 8008 The Intel 8008 ("''eight-thousand-eight''" or "''eighty-oh-eight''") is an early byte-oriented microprocessor A microprocessor is a computer processor where the data processing logic and control is included on a single integrated circuit, ...

Intel 8008
were not powerful enough (in fact several microcomputers based on Intel chips were already on the market: the Canadian company
Microsystems International Microsystems International Limited (MIL) was a telecommunications microelectronics company based in Ottawa, Ontario, Canada, founded in 1969. MIL was an early attempt to create a merchant semiconductor house by Nortel Networks (then Northern Electr ...
's CPS-1 built-in 1972 used a MIL MF7114 chip modeled on the 4004, the
Micral Micral is a series of microcomputer A microcomputer is a small, relatively inexpensive computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern computers can ...
marketed in January 1973 by the French company
R2E R, or r, is the eighteenth letter Letter, letters, or literature may refer to: Characters typeface * Letter (alphabet) A letter is a segmental symbol A symbol is a mark, sign, or word that indicates, signifies, or is understood as r ...
and the
MCM/70 The MCM/70 was a pioneering microcomputer first built in 1973 in Toronto, Ontario, Canada and released the next year. This makes it one of the first microcomputers in the world, the second to be shipped in completed form, and the first portable comp ...
marketed in 1974 by the Canadian company Micro Computer Machines); the National Semiconductor IMP-8 and
IMP-16 The IMP-16, by National Semiconductor National Semiconductor was an American American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the United States The United States of A ...
required external hardware; the
Motorola 6800 The 6800 ("''sixty-eight hundred''") is an 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the M6800 Microcomputer System that also included serial and parallel interface integrated c ...

Motorola 6800
was still in development. So he chose the 8-bit
Intel 8080 The Intel 8080 (''"eighty-eighty"'') is the second 8-bit microprocessor designed and manufactured by Intel. It first appeared in April 1974 and is an extended and enhanced variant of the earlier Intel 8008, 8008 design, although without binary ...
. Wayne Green visited MITS in August 1975 and interviewed Ed Roberts. The article has several paragraphs on the design of the Altair 8800. At that time, Intel's main business was selling memory chips by the thousands to computer companies. They had no experience in selling small quantities of microprocessors. When the 8080 was introduced in April 1974, Intel set the single unit price at $360 (About $1,700 in 2014 dollars). "That figure had a nice ring to it," recalled Intel's Dave House in 1984. "Besides, it was a computer, and they usually cost thousands of dollars, so we felt it was a reasonable price." Ed Roberts had experience in buying
OEM An original equipment manufacturer (OEM) is generally perceived as a company that produces parts and equipment that may be marketed by another manufacturer. However, the term is also used in several other ways, which causes ambiguity Ambig ...
quantities of calculator chips and he was able to negotiate a $75 price (about $350 in 2014 dollars) for the 8080 microprocessor chips. Intel made the Intellec-8 Microprocessor Development System that typically sold for a very profitable $10,000. It was functionally similar to the Altair 8800 but it was a commercial grade system with a wide selection of peripherals and development software. "Intel Corporation has announced that an interactive display console and highspeed line printer are now available for the Intellec MDS microcomputer development system. … The display console costs $2240 and the printer $3200 in quantities of 1 to 9. Delivery is in 30 days. Price of the basic Intellec MDS with 16K bytes of RAM memory, including interfaces and resident software for operating the peripherals, is $3950." Customers would ask Intel why their Intellec-8 was so expensive when that Altair was only $400. Some salesmen said that MITS was getting cosmetic rejects or otherwise inferior chips. In July 1975, Intel sent a letter to its sales force stating that the MITS Altair 8800 computer used standard Intel 8080 parts. The sales force should sell the Intellec system based on its merits and that no one should make derogatory comments about valued customers like MITS. The letter was reprinted in the August 1975 issue of MITS Computer Notes. Intel letter to its sales force. "We wish to clarify any misconception that may exist in your minds regarding the MITS ALTAIR system. This product is designed around the Intel Standard Data Sheet 8080 family." The "cosmetic defect" rumor has appeared in many accounts over the years although both MITS and Intel issued written denials in 1975. "Ed Roberts was able to get around this problem by obtaining a supply of cosmetic reject chips for about 1/3 the retail price."


The launch

For a decade, colleges had required science and engineering majors to take a course in computer programming, typically using the
FORTRAN Fortran (; formerly FORTRAN) is a general-purpose, compiled language, compiled imperative programming, imperative programming language that is especially suited to numerical analysis, numeric computation and computational science, scientific com ...

FORTRAN
or
BASIC BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming language In computer science Computer science deals with the theoretical foundations of information, algorithms and the ar ...

BASIC
languages. Describes the introductory computer science courses at the University of Waterloo. This meant there was a sizable customer base who knew about computers. In 1970, electronic calculators were not seen outside of a laboratory, but by 1974 they were a common household item. Calculators and video games like ''
Pong ''Pong'' is a table tennis Table tennis, also known as ping-pong and whiff-whaff, is a sport in which two or four players hit a lightweight ball, also known as the ping-pong ball, back and forth across a table using small rackets. The game ...

Pong
'' introduced computer power to the general public. Electronics hobbyists were moving on to digital projects such as digital voltmeters and frequency counters. The Altair had enough power to be actually useful, and was designed as an expandable system that opened it up to all sorts of applications. Ed Roberts optimistically told his banker that he could sell 800 computers, while in reality they needed to sell 200 over the next year just to break even. When readers got the January issue of ''Popular Electronics'', MITS was flooded with inquiries and orders. They had to hire extra people just to answer the phones. In February MITS received 1,000 orders for the Altair 8800. The quoted delivery time was 60 days but it was months before they could meet that. Roberts focused on delivering the computer; all of the options would wait until they could keep pace with the orders. MITS claimed to have delivered 2,500 Altair 8800s by the end of May. "There was a subsequent article in February's Popular Electronics and the MITS people knew the Altair was here to stay. During that month alone, over 1,000 mainframes were sold. Datamation, March 1975." "By the end of May, MITS had shipped over 2,500 Altair 8800's" The number was over 5,000 by August 1975. MITS had under 20 employees in January but had grown to 90 by October 1975. "We had less than 20 employees when we introduced the Altair and now we have grown to 90 as a result of our Altair customers." Roberts also discussed the problems with the 4K dynamic RAM boards. Customers got a $50 refund. The Altair 8800 computer was a break-even sale for MITS. They needed to sell additional memory boards, I/O boards and other options to make a profit. The system came with a "1024 word" (1024 byte) memory board populated with 256 bytes. The BASIC language was announced in July 1975 and it required one or two 4096 word memory boards and an interface board. MITS Price List, ''Popular Electronics'', August 1975. *4K BASIC language (when purchased with Altair, 4096 words of memory and interface board) $60 *8K BASIC language (when purchased with Altair, two 4096-word memory boards and interface board) $75 MITS had no competition in the US for the first half of 1975. Their 4K memory board used dynamic RAM and it had several design problems. The delay in shipping optional boards and the problems with the 4K memory board created an opportunity for outside suppliers. An enterprising Altair owner, Robert Marsh, designed a 4K static memory that was plug-in compatible with the Altair 8800 and sold for $255. His company was
Processor Technology Processor Technology Corporation was a personal computer company founded in April 1975 by Gary Ingram and Bob Marsh in Berkeley, California Berkeley ( ) is a city on the eastern shore of San Francisco Bay in northern Alameda County, California, ...
, one of the most successful Altair compatible board suppliers. Their advertisement in the July 1975 issue of ''Popular Electronics'' promised interface and PROM boards in addition to the 4K memory board. They would later develop a popular video display board that would plug directly into the Altair. A consulting company in San Leandro, California, IMS Associates Inc., wanted to purchase several Altair computers but the long delivery time convinced them that they should build their own computers. In the October 1975 ''Popular Electronics'', a small advertisement announced the
IMSAI 8080 The IMSAI 8080 was an early microcomputer A microcomputer is a small, relatively inexpensive computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern compu ...
computer. The ad noted that all boards were "
plug compatible Plug compatible refers to "hardware that is designed to perform exactly like another vendor's product." The term PCM was originally applied to manufacturers who made replacements for IBM peripherals. Later this term was used to refer to IBM-compatib ...
" with the Altair 8800. The computer cost $439 for a kit. The first 50 IMSAI computers shipped in December 1975. "Later that day, December 16
975 Year 975 ( CMLXXV) was a common year starting on Friday A common year starting on Friday is any non-leap year (i.e. a year with 365 days) that begins on Friday, 1 January, and ends on Friday, 31 December. Its dominical letter hence is C. The ...
United Parcel Service picked up the first shipment of 50 IMS computer kits for delivery to customers."
The IMSAI 8080 computer improved on the original Altair design in several areas. It was easier to assemble: The Altair required 60 wire connections between the front panel and the mother board (
backplane A backplane (or "backplane system") is a group of electrical connector An electrical connector is an electromechanical device used to join electrical conductors and create an electrical circuit An electrical network is an interconnec ...

backplane
.) The IMSAI motherboard had 18 slots. The MITS motherboard consisted of 4 slots segments that had to be connected together with 100 wires. The IMSAI also had a larger power supply to handle the increasing number of expansion boards used in typical systems. The IMSAI advantage was short lived because MITS had recognized these shortcomings and developed the Altair 8800B which was introduced in June 1976. In 1977, Pertec Computer Corporation purchased MITS and began to market the computer, without changes (except for branding), as the PCC 8800 in 1978.


Description

In the first design of the Altair, the parts needed to make a complete machine would not fit on a single
motherboard A motherboard (also called mainboard, main circuit board, or mobo) is the main printed circuit board A printed circuit board (PCB) is a laminated sandwich structure of conductive and insulating layers. PCBs have two complementary functions. ...

motherboard
, and the machine consisted of four boards stacked on top of each other with stand-offs. Another problem facing Roberts was that the parts needed to make a truly useful computer weren't available, or wouldn't be designed in time for the January launch date. So during the construction of the second model, he decided to build most of the machine on removable cards, reducing the
motherboard A motherboard (also called mainboard, main circuit board, or mobo) is the main printed circuit board A printed circuit board (PCB) is a laminated sandwich structure of conductive and insulating layers. PCBs have two complementary functions. ...

motherboard
to nothing more than an interconnect between the cards, a
backplane A backplane (or "backplane system") is a group of electrical connector An electrical connector is an electromechanical device used to join electrical conductors and create an electrical circuit An electrical network is an interconnec ...

backplane
. The basic machine consisted of five cards, including the
CPU A central processing unit (CPU), also called a central processor, main processor or just processor, is the electronic circuit File:PExdcr01CJC.jpg, 200px, A circuit built on a printed circuit board (PCB). An electronic circuit is composed of ...

CPU
on one and memory on another. He then looked for a cheap source of connectors, and came across a supply of 100-pin
edge connector Two 44-pin edge connector sockets (blue objects) and matching circuit board. The Edge connector is long, with 22 contacts on each side An edge connector is the portion of a printed circuit board A printed circuit board (PCB) mechanically su ...
s. The
S-100 bus The S-100 bus or Altair bus, IEEE 696-1983 ''(withdrawn)'', is an early computer bus In computer architecture In computer engineering, computer architecture is a set of rules and methods that describe the functionality, organization, and ...
was eventually acknowledged by the professional computer community and adopted as the IEEE-696 computer bus standard. The
Altair bus The S-100 bus or Altair bus, IEEE 696-1983 ''(withdrawn)'', is an early computer bus In computer architecture In computer engineering, computer architecture is a set of rules and methods that describe the functionality, organization, and ...
consists of the pins of the
Intel 8080 The Intel 8080 (''"eighty-eighty"'') is the second 8-bit microprocessor designed and manufactured by Intel. It first appeared in April 1974 and is an extended and enhanced variant of the earlier Intel 8008, 8008 design, although without binary ...
run out onto the backplane. No particular level of thought went into the design, which led to such disasters as
shorting In finance Finance is the study of financial institutions, financial markets and how they operate within the financial system. It is concerned with the creation and management of money and investments. Savers and investors have money avail ...

shorting
from various power lines of differing
voltage Voltage, electric potential difference, electric pressure or electric tension is the difference in electric potential The electric potential (also called the ''electric field potential'', potential drop, the electrostatic potential) is the ...

voltage
s being located next to each other. Another oddity was that the system included two unidirectional
8-bit In computer architecture, 8-bit integer (computer science), integers or other data#Uses of data in computing, data units are those that are 8 bits wide (1 octet). Also, 8-bit central processing unit, CPU and arithmetic logic unit, ALU arch ...
data buses, when the normal practice was for a single bidirectional bus (this oddity did, however, allow a later expansion of the S-100 standard to 16 bits bidirectional by using both 8-bit buses in parallel). A deal on power supplies led to the use of +8 and +18V, which had to be locally regulated on the cards to TTL (+5V) or
RS-232 In telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, Optical system, optical, or other Electromagnetism, electromagnetic systems. It has its origin in the desire of ...
(+12V) standard voltage levels. The Altair shipped in a two-piece case. The backplane and power supply were mounted on a base plate, along with the front and rear of the box. The "lid" was shaped like a C, forming the top, left, and right sides of the box. The
front panel Front may refer to: Arts, entertainment, and media Films * ''The Front'' (1943 film), a 1943 Soviet drama film * ''The Front ''The Front'' is a 1976 comedy-drama Comedy-drama, or dramedy, is a genre of dramatic works that combines element ...

front panel
, which was inspired by the
Data General Nova The Data General Nova is a series of 16-bit 16-bit microcomputers are computers in which 16-bit microprocessors were the norm. A 16-bit register can store 216 different values. The range (computer programming), range of integer values that ca ...
minicomputer, included a large number of
toggle switch In electrical engineering Electrical engineering is an engineering discipline concerned with the study, design, and application of equipment, devices, and systems which use electricity, electronics The field of electronics is a branch of p ...
es to feed
binary Binary may refer to: Science and technology Mathematics * Binary number In mathematics and digital electronics, a binary number is a number expressed in the base-2 numeral system or binary numeral system, which uses only two symbols: ty ...
data directly into the memory of the machine, and a number of red
LED An LED A light-emitting diode (LED) is a semiconductor A semiconductor material has an Electrical resistivity and conductivity, electrical conductivity value falling between that of a Electrical conductor, conductor, such as metallic ...
s to read those values back out. Ed Roberts said: "We had a Nova 2 by Data General in the office that we sold timeshare on …The front panel on an Altair essentially models every switch that was on the Nova 2. We had that machine to look at. The switches are pretty much standard of any front panel machine. It would have taken forever if we would have had to re-decide where every switch had to go. " Programming the Altair via the front panel could be a tedious and time-consuming process. Programming required the toggling of the switches to positions corresponding to the desired 8080 microprocessor instruction or
opcode In computing, an opcode (abbreviated from operation code, also known as instruction machine code, instruction code, instruction syllable, instruction parcel or opstring) is the portion of a machine code, machine language instruction (computer sc ...
in binary, then used the 'DEPOSIT NEXT' switch to load that instruction into the next address of the machine's memory. This step was repeated until all the opcodes of a presumably complete and correct program were in place. The only output from the programs was the patterns of lights on the panel. Nevertheless, many were sold in this form. Development was already underway on additional cards, including a
paper tape Five- and eight-hole punched paper tape file:Harwell-dekatron-witch-10.jpg, Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop Punched tape or perforated pape ...

paper tape
reader for storage, additional
RAM Random-access memory (RAM; ) is a form of computer memory In computing Computing is any goal-oriented activity requiring, benefiting from, or creating computing machinery. It includes the study and experimentation of algorithmic proces ...
cards, and an
RS-232 In telecommunications Telecommunication is the transmission of information by various types of technologies over wire, radio, Optical system, optical, or other Electromagnetism, electromagnetic systems. It has its origin in the desire of ...
interface to connect to a proper Teletype terminal.


Software


Altair BASIC

Ed Roberts received a letter from
Traf-O-Data Traf-O-Data was a business partnership between Bill Gates William Henry Gates III (born October 28, 1955) is an American business magnate, software developer, investor, author, landowner and philanthropist. He is a co-founder of Microsof ...
asking if he would be interested in buying its
BASIC BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of general-purpose, high-level programming language In computer science Computer science deals with the theoretical foundations of information, algorithms and the ar ...

BASIC
programming language A programming language is a formal language In logic, mathematics, computer science, and linguistics, a formal language consists of string (computer science), words whose symbol (formal), letters are taken from an alphabet (computer science) ...

programming language
for the machine. He called the company and reached a private home, where no one had heard of anything like BASIC. In fact the letter had been sent by
Bill Gates William Henry Gates III (born October 28, 1955) is an American business magnate A business magnate is someone who has achieved great success and enormous wealth through the ownership of multiple lines of enterprise. The term character ...
and
Paul Allen Paul Gardner Allen (January 21, 1953 – October 15, 2018) was an American business magnate, computer programmer, researcher, investor, and philanthropist. He co-founded Microsoft, Microsoft Corporation with childhood friend Bill Gates in 19 ...

Paul Allen
from the
Boston Boston (, ), officially the City of Boston, is the capital city, capital and List of municipalities in Massachusetts, most populous city of the Commonwealth (U.S. state), Commonwealth of Massachusetts in the United States and 21st List of Unit ...

Boston
area, and they had no BASIC yet to offer. When they called Roberts to follow up on the letter he expressed his interest, and the two started work on their BASIC interpreter using a self-made
simulator A simulation is the imitation of the operation of a real-world process or system over time. Simulations require the use of models; the model represents the key characteristics or behaviors of the selected system or process, whereas the simula ...
for the 8080 on a
PDP-10 Digital Equipment Corporation Digital Equipment Corporation (DEC ), using the Digital, was a major American company in the from the 1960s to the 1990s. The company was co-founded by and in 1957. Olsen was president until forced to resi ...
minicomputer. They figured they had 30 days before someone else beat them to the punch, and once they had a version working on the simulator, Allen flew to Albuquerque to deliver the program,
Altair BASIC Altair BASIC is a discontinued interpreter for the BASIC programming language BASIC (Beginners' All-purpose Symbolic Instruction Code) is a family of General-purpose programming language, general-purpose, high-level programming languages whos ...
(aka MITS 4K BASIC), on a
paper tape Five- and eight-hole punched paper tape file:Harwell-dekatron-witch-10.jpg, Paper tape reader on the Harwell computer with a small piece of five-hole tape connected in a circle – creating a physical program loop Punched tape or perforated pape ...

paper tape
. The first time it was run, it displayed "READY" then Allen typed "PRINT 2+2" and it immediately printed the correct answer: "4". The game ''
Lunar Lander A lunar lander or Moon lander is a spacecraft 275px, The US Space Shuttle flew 135 times from 1981 to 2011, supporting Spacelab, ''Mir'', the Hubble Space Telescope, and the ISS. (''Columbia'' STS-1">maiden launch, which had a white exter ...
'' was entered in and this worked as well. Gates soon joined Allen and formed
Microsoft Microsoft Corporation is an American multinational corporation, multinational technology company, technology corporation which produces Software, computer software, consumer electronics, personal computers, and related services. Its best-know ...

Microsoft
, then spelled "Micro-Soft".


Altair DOS

Announced in late 1975, it started shipping in August 1977.


See also

*
SIMH SIMH is a highly portable, multi-system emulator emulates the command-line interface A command-line interface (CLI) processes commands to a computer program in the form of lines of text. The program which handles the interface is called ...
emulates Altair 8800 with both 8080 and
Z80 The Z80 is an 8-bit In computer architecture, 8-bit integer (computer science), integers or other data#Uses of data in computing, data units are those that are 8 bits wide (1 octet). Also, 8-bit central processing unit, CPU and arithmeti ...

Z80
. *
IMSAI 8080 The IMSAI 8080 was an early microcomputer A microcomputer is a small, relatively inexpensive computer A computer is a machine that can be programmed to carry out sequences of arithmetic or logical operations automatically. Modern compu ...
*


References


Further reading


Books

* * * * * Chapter 6 "Mechanics: Kits & Microcomputers"


Magazines

* * * * *


External links

* {{cite web, title=Altair 8800 , publisher=New Mexico Museum of Natural History and Science , url=http://startup.nmnaturalhistory.org/gallery/item.php?ii=26 , access-date=2007-12-18 , url-status=dead , archive-url=https://web.archive.org/web/20120323162008/http://startup.nmnaturalhistory.org/gallery/item.php?ii=26 , archive-date=March 23, 2012
MITS Altair 8800 exhibit at old-computers.com's virtual computer museum

Virtual Altair Museum

Altair 8800 images and information at vintage-computer.com



Maker of a hardware emulation of the 8800 running on an Atmel AVR 8515

Altair 8800 Clone

True-to-life MITS Altair 8800 online simulator
Early microcomputers Computer-related introductions in 1974 S-100 machines 8-bit computers