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I [[corsa allo spazio|voli spaziali]] e la [[programma Apollo|corsa alla Luna]] degli [[anni 1960|anni Sessanta]] avevano reso il razzimodellismo un hobby molto popolare. Roberts, Mims, Cagle e Zaller pensavano che costruire e vendere kit elettronici agli appassionati di questo hobby avrebbe fruttato molto, ma così non fu. Nonostante gli articoli pubblicati su ''Popular Electronics'', una rivista con una grossa tiratura, la neonata società aveva venduto solo un centinaio di kit.
Zaller, a quel tempo, aveva già smesso di partecipare attivamente agli affari e Mims aveva lasciato l'Aeronautica e voleva dedicarsi a tempo pieno al mestiere di scrittore. Roberts rilevò quindi le quote degli altri 3 soci per 600$ in contanti e 350$ di materiali ed assunse il controllo della società.<ref>Mims (1986), 34–36.</ref> Per rilanciare gli affari pensò quindi di entrare nel mercato delle calcolatrici elettroniche.<!--
[[File:MITS Calculator 1200 Series 1973.jpg|thumb|right| Sales had reached $100,000 per month when this advertisement ran in March 1973.]]
[[File:MITS Calculator 1200 Series 1973.jpg|thumb|right|Un annuncio della MITS Calculator 1200 del 1973. A quel tempo il fatturato della ditta era di 100.000$ mensili.]]
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Roberts si era interessato ai computer quando frequentava le scuole superiori ed aveva costruito per diletto un semplice computer digitale. Ma la sua prima, vera, esperienza con i computer la ebbe quando era presso l'Università dell'Oklahoma, dove gli studenti di ingegneria avevano libero accesso ad un [[IBM 1620]]. Presso il suo ufficio alla base aerea di Kirtland Roberts aveva invece un [[Hewlett-Packard 9100A]], un calcolatore programmabile.
Ed Roberts' interest in computers began in high school when he built a simple digital computer from relays. His first real experience with computers came while at Oklahoma State University where engineering students had free access to an [[IBM 1620]] computer. Roberts' office at Weapons Laboratory had the state of the art [[Hewlett-Packard 9100A]] programmable calculator in 1968. In July 1970, a semiconductor company, Electronic Arrays, announced a set of six LSI ICs that would make a four-function calculator.<ref name = "EAS100">{{cite journal | title = New Products: Do-it-yourself Electronic Calculator | journal = Computer | volume = 3 | issue = 6 | pages = pp. 38–41 | publisher = IEEE | date = November 1970 | url = http://books.google.com/?id=GJ2wAAAAIAAJ&q=%22Electronic+Arrays%22+Calculator | doi = 10.1109/C-M.1970.216730 | quote = Electronic Arrays has developed the EAS100, a set of MOS LSI circuits for a 16 digit calculator with 8 digit display capability.}}</ref><ref name = "Calculator Patent">{{US patent reference | number = 3800129 | y = 1974 | m = 03 | d = 26 | inventor = Richard H. Umstattd | title = MOS Desk Calculator}} The Electronic Arrays, Inc. calculator chip set that was used in the MITS 816 calculator.</ref> Roberts was determined to design a calculator kit.
Roberts decise quindi di realizzare una calcolatrice in kit utilizzando un gruppo di 6 [[Circuito_integrato#Scala_di_integrazione|circuiti integrati LSI]] prodotti da ''Electronic Arrays''<ref name = "EAS100">{{cita pubblicazione | titolo = New Products: Do-it-yourself Electronic Calculator | rivista = Computer | volume = 3 | numero = 6 | pagine = 38–41 | editore = IEEE | data = novembre 1970 | url = http://books.google.com/?id=GJ2wAAAAIAAJ&q=%22Electronic+Arrays%22+Calculator}}</ref> e produsse la ''MITS 816'', una calcolatrice capace di 4 funzioni (quelle permesse dagli integrati utilizzati): somma, sottrazione, moltiplicazione e divisione. Il display visualizzava solo 8 cifre ma i calcoli erano eseguiti con una precisione a 16 cifre. Il kit era venduto a 179$ da assemblare oppure a 275$ già montato. La MITS 816 apparve sulla copertina del numero di novembre del 1971 di ''Popular Electronics''.<ref name = "MITS 816">{{cita pubblicazione | cognome = Roberts | nome = Ed | data = novembre 1971 | titltitolo = Electronic desk calculator you can build | rivista = Popular Electronics | volume = 35 | numero = 5 | pagine = 27–32 }}</ref>
To fund the new project, Roberts sold 15% of MITS to fellow Air Force officer, Lieutenant William Yates. He also got an investment from another Weapons Laboratory officer, Major Ed Laughlin. Several other officers and scientist at the lab were interested in this state of the art calculator kit and helped with the design. Forrest Mims wrote the assembly manual in return for a calculator kit.
Grazie alle ottime vendite del kit, MITS potè pubblicizzare la calcolatrice su molte riviste, quali ''Radio-Electronics'', ''Popular Electronics'' e ''Scientific American''. Sul numero di giugno del [[1972]] di ''Radio-Electronics'' MITS annunciava il modello ''1440'': questa calcolatrice era capace di visualizzare 14 cifre, aveva una memoria e poteva eseguire il calcolo della [[radice quadrata]]. Il kit era in vendita a 199,95$ da assemblare ed a 249,95$ già assemblata. Il prezzo della 816 fu portato a 149,95$. Il fatturato mensile raggiunse i 100.000 dollari nel mese di marzo del [[1973]] e la società si trasferì in una struttura di 930 metri quadrati.<ref name = "Albq Tribune Apr 1973">{{cita news | cognome = Lucas | nome = Urith | titolo = Albq calculator firm to expand plant, triple number of employees | pubblicazione = The Albuquerque Tribune | pagine = C14 | data = 20 aprile 1973}}</ref>
The MITS 816 was known as a "four-function" calculator; it could add, subtract, multiply and divide. The display was only 8-digits but the calculations were done to 16-digits of accuracy. The custom molded case gave the kit a professional appearance; the kit was $179 and an assembled unit was $275. The MITS 816 was featured on the November 1971 cover of ''Popular Electronics''.<ref name = "MITS 816">{{cite journal | last = Roberts | first = Ed | date = November 1971 | title = Electronic desk calculator you can build | journal = Popular Electronics | volume = 35 | issue = 5 | pages = pp. 27–32 }}</ref> Thousands of calculator orders came in each month, in contrast to poor results for previous kits that MITS had offered.<ref name = "Albq Journal Oct 1971"> {{cite news | last = Cliff | first = W. Wilson | title = Little Firm in City Making Big Name with Calculator | work = Albuquerque Journal | page = G-2 | quote = But hundreds of thousands of electronics enthusiasts the world over have read about MITS within the last 10 days and no less than 200 already bought the light-weight 16-digit electronic calculator… | date = October 31, 1971}}</ref>
TheAlla steadyfine flowdel of1972 calculatorfu salespresentato allowedil MITS to run full page advertisements inmodello ''Radio-Electronics7400'', ''Popularcapace Electronics''di andfunzioni ''Scientific[[trigonometria|trigonometriche]], American''.conversione Inda thecoordinate Junerettangolari 1972a ''Radio-Electronics''[[coordinate polari|polari]], MITS2 announcedmemorie ae 14con digituno calculator[[stack]] (Modelcon 1440)fino witha memory7 andlivelli squaredi rootdati. functionUn forkit $199.95di kituna and7400 $249.95con assembled.stack Thea original3 816livelli kitcostava was$299,95$ reducedda fromassemblare $179mentre touna $149.95.calcolatrice Bothcon calculators7 couldlivelli bedi controlledstack bygià upcomingassemblata programmingcostava unit419,95$.<ref name = "RE JuneDecember 1972">{{citecita journalpubblicazione | titletitolo = A New Standard! MITS announces7400 ourScientific forthand generation.Engineering Calculator | journalrivista = Radio-Electronics | volume = 43 | issuenumero = 612 | pagepagine = p. 1317 | datedata = Junedicembre 1972}} Full page advertisement of the Model 1440 calculator.</ref>
Nel mese di marzo del [[1974]] MITS presentò il ''Programmer'', un accessorio che poteva essere collegato ai suoi più recenti prodotti e permetteva di programmare le calcolatrici mediante codici [[Sistema numerico esadecimale|esadecimali]]. Le funzioni erano limitate rispetto ad una calcolatrice programmabile quale la HP 9830, ma una MITS 7440 con il Programmer costavano solo 400$, una cifra di molto inferiore.
The monthly sales reached $100,000 in March 1973 and MITS moved to larger building with 10,000 square feet (930 square meters) of space.<ref name = "Albq Tribune Apr 1973">{{cite news | last = Lucas | first = Urith | title = Albq calculator firm to expand plant, triple number of employees | work = The Albuquerque Tribune | page = C14 | date = April 20, 1973}} Summary: MITS to move to the Cal-Lin Building, 6328 Linn NE in May. Now at 5404 Coal SE. Employment is expected to rise from 62 to 180 or 200. Company will have 10,000 square feet on one floor. Calculator sales reached $100,000 in March.</ref> To meet the demand for assembled calculators, an automated [[Wave soldering | wave solder machine]] was installed.<ref>Roberts (1974), 74–83. The "Calculator Manufacturing" section describes in detail how MITS produces calculators and has 10 photographs of the process.</ref> In 1973 MITS was selling every calculator they could make, 110 employees worked in two shifts assembling calculators.<ref>Young (1998), 152–153.</ref>
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The functionality of calculator ICs increased at a rapid pace and Roberts was designing and producing new models. The MITS 7400 scientific and engineering calculator was introduced in December 1972. It featured trigonometric functions, polar to rectangular conversion, two memories, and up to a seven-level [[Stack (data structure)|stack]]. A kit with a three-level stack was $299.95 and an assembled unit with a seven-level stack was $419.95.<ref name = "RE December 1972">{{cite journal | title = A New Standard! MITS 7400 Scientific and Engineering Calculator | journal = Radio-Electronics | volume = 43 | issue = 12 | page = p. 17 | date = December 1972}} Full page advertisement of the Model 7400 scientific calculator.</ref> The next month the Series 1200 four-function pocket calculators were announced. The six-digit model was $59.95 and the twelve-digit model was $99.95.
The Programmer accessory had been mentioned in the earliest advertisement but it was not featured until March 1974. This was the same size as a desktop calculator and could hold 256 programming steps. (It could be expanded to 512 steps.) It was limited to emulating calculator key presses and simple sequence branching. The programming was done by entering [[hexadecimal]] key codes. The combination of the MITS 7440 calculator and the programmer was not nearly as sophisticated as the [[HP 9800 series desktop computers | HP 9830 calculator]] but $400 for both kits was a fraction of the HP price.
=== MITS calculators ===
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