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Thehistory of computing hardware starting at 1960 is marked by the conversion fromvacuum tube tosolid-state devices such astransistors and thenintegrated circuit (IC) chips. Around 1953 to 1959, discrete transistors started being considered sufficiently reliable and economical that they made further vacuum tube computersuncompetitive.Metal–oxide–semiconductor (MOS)large-scale integration (LSI) technology subsequently led to the development ofsemiconductor memory in the mid-to-late 1960s and then themicroprocessor in the early 1970s. This led to primarycomputer memory moving away frommagnetic-core memory devices to solid-state static and dynamic semiconductor memory, which greatly reduced the cost, size, and power consumption of computers. These advances led to the miniaturizedpersonal computer (PC) in the 1970s, starting withhome computers anddesktop computers, followed bylaptops and thenmobile computers over the next several decades.

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For the purposes of this article, the term "second generation" refers to computers using discrete transistors, even when the vendors referred to them as "third-generation". By 1960 transistorized computers were replacing vacuum tube computers, offering lower cost, higher speeds, and reduced power consumption. The marketplace was dominated byIBM and the seven dwarfs:

• IBM
• TheBUNCH
  • Burroughs
  • UNIVAC
  • NCR
  • Control Data Corporation (CDC)
  • Honeywell
• General Electric
• RCA.

Some examples of 1960s second generation computers from those vendors are:

• theIBM 1401, theIBM 7090/7094, and theIBM System/360;
• theBurroughs 5000 series;
• theUNIVAC 1107;
• theNCR 315;
• theCDC 1604 and theCDC 3000 series;
• theHoneywell 200, Honeywell 400, andHoneywell 800;
• theGE-400 series and theGE-600 series;
• the RCA 301, 3301,501, and theSpectra 70 series.

However, some smaller companies made significant contributions. Also, towards the end of the second generationDigital Equipment Corporation (DEC) was a serious contender in the small and medium machine marketplace.

Meanwhile, second-generation computers were also being developed in the USSR as, e.g., theRazdan family of general-purpose digital computers created at theYerevan Computer Research and Development Institute.

The second-generation computer architectures initially varied; they included character-baseddecimal computers,sign-magnitude decimal computers with a 10-digit word, sign-magnitude binary computers, andones' complement binary computers, although Philco, RCA, and Honeywell, for example, had some computers that were character-based binary computers andDigital Equipment Corporation (DEC) and Philco, for example, hadtwo's complement computers. With the advent of the IBMSystem/360, two's complement became the norm for new product lines.

The most common word sizes for binary mainframes were 36 and 48 bits, although entry-level and midrange machines used smaller words, e.g.,12 bits,18 bits,24 bits,30 bits. All but the smallest machines had asynchronousI/O channels andinterrupts. Typically binary computers with word size up to 36 bits had one instruction per word, binary computers with 48 bits per word had two instructions per word and the CDC 60-bit machines could have two, three, or four instructions per word, depending on the instruction mix; the BurroughsB5000,B6500/B7500 and B8500 lines are notable exceptions to this.

First-generation computers with data channels (I/O channels) had a basic DMA interface to the channel cable. The second generation saw both simpler, e.g., channels on theCDC 6000 series had no DMA, and more sophisticated designs, e.g., the 7909 on theIBM 7090 had limited computational, conditional branching and interrupt system.

By 1960,magnetic core was the dominant memory technology, although there were still some new machines usingdrums anddelay lines during the 1960s.Magnetic thin film androd memory were used on some second-generation machines, but advances in core technology meant they remained niche players until semiconductor memory displaced both core and thin film.

In the first generation, word-oriented computers typically had a singleaccumulator and an extension, referred to as, e.g., Upper and Lower Accumulator, Accumulator and Multiplier-Quotient (MQ) register. In the second generation, it became common for computers to have multiple addressable accumulators. On some computers, e.g.,PDP-6, the same registers served as accumulators andindex registers, making them an early example ofgeneral-purpose registers.

In the second generation there was considerable development of newaddress modes, including truncated addressing on, e.g., thePhilcoTRANSAC S-2000, theUNIVAC III, and automatic index register incrementing on, e.g., the RCA 601,UNIVAC 1107, and theGE-600 series. Althoughindex registers were introduced in the first generation under the nameB-line, their use became much more common in the second generation. Similarly,indirect addressing became more common in the second generation, either in conjunction with index registers or instead of them. While first-generation computers typically had a small number of index registers or none, several lines of second-generation computers had large numbers of index registers, e.g.,Atlas,Bendix G-20,IBM 7070.

The first generation had pioneered the use of special facilities for calling subroutines, e.g.,TSX on theIBM 709. In the second generation, such facilities were ubiquitous; some examples are:

Automatically record the next sequential instruction (NSI) in a register for all or most successful branch instructions

The Jump Address (JA) Register on the Philco TRANSAC S-2000

The Sequence History (SH) and Cosequence History (CSH) registers on theHoneywell 800

The B register on anIBM 1401 with the indexing feature

Automatically record the NSI at a standard memory location following all or most successful branches

Store P (STP) locations on RCA 301, 3301 and 501

STICC on the RCA 601 is relative to the lower bound register

Call instructions that save the NSI in the first word of the subroutine

Return Jump (RJ) on theUNIVAC 1107

Return Jump (RJ) onCDC 3600 andCDC 6000 series

Jump to Subroutine (JSR) on theDECPDP-6 andPDP-10

Call instructions that save the NSI in an implicit or explicit register

Branch and Load Location in Index Word (BLX) on theIBM 7070

Transfer and Set indeX (TSX) on theIBM 7090

Jump and Save PC (JSP) on theDECPDP-6 andPDP-10

Transfer and Set Xn (TSXn) on theGE-600 series

Branch and Link (BAL) on theIBM System/360

Call instructions that use an index register as astack pointer and push return information onto the stack

Push jump (PUSHJ) on theDECPDP-6

Implicit call with return information pushed onto the stack

Program descriptors on the BurroughsB5000 line

Program descriptors on the BurroughsB6500 line

The second generation saw the introduction of features intended to supportmultiprogramming andmultiprocessor configurations, including master/slave (supervisor/problem) mode, storage protection keys, limit registers, protection associated with address translation, andatomic instructions.

Second generation supercomputers were substantially faster than most contemporary mainframes. Some of the technologies developed in order to achieve the desired performance are now used in commodity computers.

The mass increase in the use of computers accelerated withThird Generation computers starting around 1966 in the commercial market. These generally relied on early (sub-1000 transistor)integrated circuit technology. The third generation ends with themicroprocessor-based fourth generation.

In 1958,Jack Kilby atTexas Instruments invented thehybrid integrated circuit (hybrid IC),^[1] which had external wire connections, making it difficult to mass-produce.^[2] In 1959,Robert Noyce atFairchild Semiconductor invented themonolithic integrated circuit (IC) chip.^[3][2] It was made ofsilicon, whereas Kilby's chip was made ofgermanium. The basis for Noyce's monolithic IC was Fairchild'splanar process, which allowed integrated circuits to be laid out using the same principles as those ofprinted circuits. The planar process was developed by Noyce's colleagueJean Hoerni in early 1959, based on the siliconsurface passivation andthermal oxidation processes developed byCarl Frosch and Lincoln Derrick in 1955 and 1957.^{[4][5][6][7][8][9]}

Computers using IC chips began to appear in the early 1960s. For example, the 1961 Semiconductor Network Computer (Molecular Electronic Computer, Mol-E-Com),^[10][11][12] the first monolithicintegrated circuit^[13][14][15] general purpose computer (built for demonstration purposes, programmed to simulate a desk calculator) was built byTexas Instruments for theUS Air Force.^{[16][17][18][19]}

Some of their early uses were inembedded systems, notably used byNASA for theApollo Guidance Computer, by the military in theLGM-30 Minutemanintercontinental ballistic missile, the Honeywell ALERT airborne computer,^[20][21] and in theCentral Air Data Computer used for flight control in theUS Navy'sF-14A Tomcat fighter jet.

An early commercial use was the 1965SDS 92.^[22][23] IBM first used ICs in computers for the logic of the System/360 Model 85 shipped in 1969 and then made extensive use of ICs in itsSystem/370 which began shipment in 1971.

The integrated circuit enabled the development of much smaller computers. Theminicomputer was a significant innovation in the 1960s and 1970s. It brought computing power to more people, not only through more convenient physical size but also through broadening the computer vendor field.Digital Equipment Corporation became the number two computer company behind IBM with their popularPDP andVAX computer systems. Smaller, affordable hardware also brought about the development of important newoperating systems such asUnix.

In November 1966,Hewlett-Packard introduced the2116A^[24][25] minicomputer, one of the first commercial 16-bit computers. It used CTμL (Complementary Transistor MicroLogic)^[26] in integrated circuits fromFairchild Semiconductor. Hewlett-Packard followed this with similar 16-bit computers, such as the 2115A in 1967,^[27] the 2114A in 1968,^[28] and others.

In 1969,Data General introduced theNova and shipped a total of 50,000 at $8,000 each. The popularity of 16-bit computers, such as the Hewlett-Packard 21xx series and the Data General Nova, led the way towardword lengths that were multiples of the8-bitbyte. The Nova was first to employmedium-scale integration (MSI) circuits from Fairchild Semiconductor, with subsequent models using large-scale integrated (LSI) circuits. Also notable was that the entirecentral processor was contained on one 15-inchprinted circuit board.

Large mainframe computers used ICs to increase storage and processing abilities. The 1965IBM System/360mainframe computer family are sometimes called third-generation computers; however, their logic consisted primarily ofSLThybrid circuits, which contained discrete transistors and diodes interconnected on a substrate with printed wires and printed passive components; the S/360 M85 and M91 did use ICs for some of their circuits. IBM's 1971System/370 used ICs for their logic, and later models usedsemiconductor memory.

By 1971, theILLIAC IV supercomputer was the fastest computer in the world, using about a quarter-million small-scaleECL logic gate integrated circuits to make up sixty-four parallel data processors.^[29]

Third-generation computers were offered well into the 1990s; for example the IBM ES9000 9X2 announced April 1994^[30] used 5,960 ECL chips to make a 10-way processor.^[31] Other third-generation computers offered in the 1990s included theDEC VAX 9000 (1989), built from ECL gate arrays and custom chips,^[32] and theCray T90 (1995).

Third-generationminicomputers were essentially scaled-down versions ofmainframe computers, designed to perform similar tasks but on a smaller and more accessible scale. In contrast, the fourth generation's origins are fundamentally different, as it is based on themicroprocessor—a computer processor integrated onto a singlelarge-scale integration (LSI)MOS integrated circuit chip.^[33]

Microprocessor-based computers were originally very limited in their computational ability and speed and were in no way an attempt to downsize the minicomputer. They were addressing an entirely different market.

Processing power and storage capacities have grown beyond all recognition since the 1970s, but the underlying technology has remained basically the same of large-scale integration (LSI) orvery-large-scale integration (VLSI) microchips, so it is widely regarded that most of today's computers still belong to the fourth generation.

The microprocessor has origins in theMOS integrated circuit (MOS IC) chip.^[33] The MOS IC wasfabricated by Fred Heiman and Steven Hofstein atRCA in 1962.^[34] Due to rapidMOSFET scaling, MOS IC chips rapidly increased in complexity at a rate predicted byMoore's law, leading tolarge-scale integration (LSI) with hundreds of transistors on a single MOS chip by the late 1960s. The application of MOS LSI chips tocomputing was the basis for the first microprocessors, as engineers began recognizing that a completecomputer processor could be contained on a single MOS LSI chip.^[33]

The earliest multi-chip microprocessors were theFour-Phase Systems AL1 in 1969 andGarrett AiResearchMP944 in 1970, each using several MOS LSI chips.^[33] On November 15, 1971,Intel released the world's first single-chip microprocessor, the4004, on a single MOS LSI chip. Its development was led byFederico Faggin, usingsilicon-gate MOS technology, along withTed Hoff,Stanley Mazor andMasatoshi Shima.^[35] It was developed for a Japanese calculator company calledBusicom as an alternative to hardwired circuitry, but computers were developed around it, with much of their processing abilities provided by one small microprocessor chip. ThedynamicRAM (DRAM) chip was based on the MOS DRAMmemory cell developed byRobert Dennard of IBM, offering kilobits of memory on one chip. Intel coupled the RAM chip with the microprocessor, allowing fourth generation computers to be smaller and faster than prior computers. The 4004 was only capable of 60,000 instructions per second, but its successors brought ever-growing speed and power to computers, including the Intel 8008, 8080 (used in many computers using theCP/Moperating system), and the 8086/8088 family. (The IBM personal computer (PC) and compatibles use processors that are still backward-compatible with the 8086.) Other producers also made microprocessors which were widely used in microcomputers.

The following table shows a timeline of significant microprocessor development.

The powerfulsupercomputers of the era were at the other end of the computing spectrum from themicrocomputers, and they also used integrated circuit technology. In 1976, theCray-1 was developed bySeymour Cray, who had left Control Data in 1972 to form his own company. This machine was the first supercomputer to makevector processing practical. It had a characteristic horseshoe shape to speed processing by shortening circuit paths. Vector processing uses one instruction to perform the same operation on many arguments; it has been a fundamental supercomputer processing method ever since. The Cray-1 could calculate 150 million floating-point operations per second (150megaflops). 85 were shipped at a price of $5 million each. The Cray-1 had aCPU that was mostly constructed ofSSI andMSIECL ICs.

Computers were generally large, costly systems owned by large institutions before the introduction of themicroprocessor in the early 1970s—corporations, universities, government agencies, and the like. Users were experienced specialists who did not usually interact with the machine itself, but instead prepared tasks for the computer on off-line equipment, such ascard punches. A number of assignments for the computer would be gathered up and processed inbatch mode. After the jobs had completed, users could collect the output printouts and punched cards. In some organizations, it could take hours or days between submitting a job to the computing center and receiving the output.

A more interactive form of computer use developed commercially by the middle 1960s. In atime-sharing system, multipleteleprinter and display terminals let many people share the use of onemainframe computer processor, with the operating system assigningtime slices to each user's jobs. This was common in business applications and in science and engineering.

A different model of computer use was foreshadowed by the way in which early, pre-commercial, experimental computers were used, where one user had exclusive use of a processor.^[36] Some of the first computers that might be called "personal" were earlyminicomputers such as theLINC andPDP-8, and later onVAX and larger minicomputers fromDigital Equipment Corporation (DEC),Data General,Prime Computer, and others. They originated as peripheral processors for mainframe computers, taking on some routine tasks and freeing the processor for computation.

By today's standards, they were physically large (about the size of a refrigerator) and costly (typically tens of thousands ofUS dollars), and thus were rarely purchased by individuals. However, they were much smaller, less expensive, and generally simpler to operate than the mainframe computers of the time, and thus affordable by individual laboratories and research projects. Minicomputers largely freed these organizations from thebatch processing and bureaucracy of a commercial or university computing center.

In addition, minicomputers were more interactive than mainframes, and soon had their ownoperating systems. The minicomputerXerox Alto (1973) was a landmark step in the development of personal computers, because of itsgraphical user interface,bit-mapped high-resolution screen, large internal and external memory storage,mouse, and special software.^[37]

In theminicomputer ancestors of the modern personal computer, processing was carried out by circuits with large numbers of components arranged on multiple largeprinted circuit boards. Minicomputers were consequently physically large and expensive to produce compared with later microprocessor systems. After the "computer-on-a-chip" was commercialized, the cost to produce a computer system dropped dramatically. The arithmetic, logic, and control functions that previously occupied several costlycircuit boards were now available in oneintegrated circuit which was very expensive to design but cheap to produce in large quantities. Concurrently, advances in developingsolid statememory eliminated the bulky, costly, and power-hungrymagnetic-core memory used in prior generations of computers.

In France, the company R2E (Réalisations et Etudes Electroniques) formed by five former engineers of theIntertechnique company,André Truong Trong Thi^[38][39] andFrançois Gernelle^[40] introduced in February 1973 a microcomputer, theMicral N based on theIntel 8008.^[41]Originally, the computer had been designed by Gernelle, Lacombe, Beckmann and Benchitrite for theInstitut National de la Recherche Agronomique to automate hygrometric measurements.^[42][43] The Micral N cost a fifth of the price of aPDP-8, about 8500FF ($1300).The clock of the Intel 8008 was set at 500 kHz, the memory was 16 kilobytes.A bus, called Pluribus was introduced and allowed connection of up to 14 boards.Different boards for digital I/O, analog I/O, memory, floppy disk were available from R2E.

The development of the single-chipmicroprocessor was an enormous catalyst to the popularization of cheap, easy to use, and truly personal computers. TheAltair 8800, introduced in aPopular Electronics magazine article in the January 1975 issue, at the time set a new low price point for a computer, bringing computer ownership to an admittedly select market in the 1970s. This was followed by theIMSAI 8080 computer, with similar abilities and limitations. The Altair and IMSAI were essentially scaled-down minicomputers and were incomplete: to connect a keyboard orteleprinter to them required heavy, expensive "peripherals". These machines both featured a front panel with switches and lights, which communicated with the operator inbinary. To program the machine after switching it on thebootstrap loader program had to be entered, without error, in binary, then a paper tape containing aBASIC interpreter loaded from a paper-tape reader. Keying the loader required setting a bank of eight switches up or down and pressing the "load" button, once for each byte of the program, which was typically hundreds of bytes long. The computer could run BASIC programs once the interpreter had been loaded.

TheMITS Altair, the first commercially successful microprocessor kit, was featured on the cover ofPopular Electronics magazine in January 1975. It was the world's first mass-produced personal computer kit, as well as the first computer to use anIntel 8080 processor. It was a commercial success with 10,000 Altairs being shipped. The Altair also inspired the software development efforts ofPaul Allen and his high school friendBill Gates who developed a BASICinterpreter for the Altair, and then formedMicrosoft.

The MITS Altair 8800 effectively created a new industry of microcomputers and computer kits, with many others following, such as a wave of small business computers in the late 1970s based on the Intel 8080,Zilog Z80 andIntel 8085 microprocessor chips. Most ran theCP/M-80 operating system developed byGary Kildall atDigital Research. CP/M-80 was the first popular microcomputer operating system to be used by many different hardware vendors, and many software packages were written for it, such asWordStar anddBase II.

Many hobbyists during the mid-1970s designed their own systems, with various degrees of success, and sometimes banded together to ease the job. Out of these house meetings, theHomebrew Computer Club developed, where hobbyists met to talk about what they had done, exchange schematics and software, and demonstrate their systems. Many people built or assembled their own computers as per published designs. For example, many thousands of people built theGalaksija home computer later in the early 1980s.

The Altair was influential. It came beforeApple Computer, as well asMicrosoft which produced and sold theAltair BASIC programming language interpreter, Microsoft's first product. The second generation ofmicrocomputers, those that appeared in the late 1970s, sparked by the unexpected demand for the kit computers at the electronic hobbyist clubs, were usually known ashome computers. For business use these systems were less capable and in some ways less versatile than the large business computers of the day. They were designed for fun and educational purposes, not so much for practical use. And although you could use some simple office/productivity applications on them, they were generally used by computer enthusiasts for learning toprogram and for running computer games, for which the personal computers of the period were less suitable and much too expensive. For the more technical hobbyists home computers were also used for electronically interfacing to external devices, such as controllingmodel railroads, and other general hobbyist pursuits.

The advent of the microprocessor and solid-state memory made home computing affordable. Early hobby microcomputer systems such as theAltair 8800 andApple I introduced around 1975 marked the release of low-cost 8-bit processor chips, which had sufficient computing power to be of interest to hobby and experimental users. By 1977 pre-assembled systems such as theApple II,Commodore PET, andTRS-80 (later dubbed the "1977 Trinity" byByte Magazine)^[44] began the era of mass-markethome computers; much less effort was required to obtain an operating computer, and applications such as games, word processing, and spreadsheets began to proliferate. Distinct from computers used in homes, small business systems were typically based onCP/M, until IBM introduced theIBM PC, which was quickly adopted. The PC was heavilycloned, leading to mass production and consequent cost reduction throughout the 1980s. This expanded the PC's presence in homes, replacing the home computer category during the 1990s andleading to the currentmonoculture of architecturally identical personal computers.

• History of computing hardware, before the 1960s
• Influence of the IBM PC on the personal computer market
• Timeline of computing
• History of Computer Software
• CPU design, a technical discussion of computing history
• History of operating systems
• History of the Internet
• History of the graphical user interface
• Timeline of programming languages
• Hardware description language
• Hardware abstraction layer
• Computer architecture, how computers are designed
• List of fictional computers
• Fifth generation computer
• Quantum computing
• Curta calculator
• List of pioneers in computer science
• Pirates of Silicon Valley,docudrama aboutApple Inc. andMicrosoft's early days
• Triumph of the Nerds
• Ubiquitous computing
• Internet of things
• Fog computing
• Edge computing
• Ambient intelligence
• System on a chip
• Network on a chip

• Freiberger, Paul;Swaine, Michael (2000) [1984].Fire in the Valley: The Making of the Personal Computer (2nd ed.). New York: McGraw-Hill.ISBN 0-07-135892-7.

• Stephen White's Computer history site (the above article is a modified version of his work,used with permission)
• Digital Deli, edited by Steve Ditlea, full text of the classic computer book
• Collection of old analog and digital computers at Old Computer Museum
• ZX81 Computer Online Museum
• Yahoo Computers and History
• IEEE computer history timeline (Archive from 2005)
• Links to all things Commodore
• A homebrew computer club site
• Computer History Museum
• Pictures and information on old computers
• PowerSource Online: New, Used, Refurbished, Hard to Find Parts, Equipment & Services
• History of Computers (1989–2004) in PC World excerpts
• How It Works – The Computer, 1971 and 1979 editions, by David Carey, illustrated by B. H. Robinson
• PC History Stan Veit's classic work on the history of Pre-IBM personal computers.
• WWW-VL: Internet HistoryArchived 2020-05-28 at theWayback Machine

• 20th century in computing
• 21st century in computing
• History of computing hardware
• History of computing
• History of Silicon Valley

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