Computer History 101: The Development Of The PC

Tom's Hardware and Que Publishing are partnering up to give you four chapters from Scott Mueller's Upgrading And Repairing PCs, 20th Edition. We're also giving away copies of the book to 10 lucky Tom's Hardware readers. To enter, please fill out the contest form.

The first chapter we're making available is from the beginning of Scott's book, covering the development of the PC. From the humble beginnings of mechanical adding machines to today's multi-core processors, we recount the events and innovations that took us where we are today and wrap it up with a convenient timetable showing the complete history of the PC!

In the days to come, we'll also present comprehensive looks at Magnetic Storage Principles, Local Area Networking, and Power Supplies.

The First Electronic Computer

A physicist named John V. Atanasoff (with associate Clifford Berry) is officially credited with creating the first true digital electronic computer from 1937 to 1942, while working at Iowa State University. The Atanasoff-Berry Computer (called the ABC) was the first to use modern digital switching techniques and vacuum tubes as switches, and it introduced the concepts of binary arithmetic and logic circuits. This was made legally official on October 19, 1973 when, following a lengthy court trial, U.S. Federal Judge Earl R. Larson voided the ENIAC patent of Eckert and Mauchly and named Atanasoff as the inventor of the first electronic digital computer.

Military needs during World War II caused a great thrust forward in the evolution of computers. In 1943, Tommy Flowers completed a secret British code-breaking computer called Colossus, which was used to decode German secret messages. Unfortunately, that work went largely uncredited because Colossus was kept secret until many years after the war.


Besides code-breaking, systems were needed to calculate weapons trajectory and other military functions.In 1946, John P. Eckert, John W. Mauchly, and their associates at the Moore School of Electrical Engineering at the University of Pennsylvania built the first large-scale electronic computer for the military. This machine became known as ENIAC, the Electrical Numerical Integrator and Calculator.It operated on 10-digit numbers and could multiply two such numbers at the rate of 300 products per second by finding the value of each product from a multiplication table stored in its memory. ENIAC was about 1000 times faster than the previous generation of electromechanical relay computers.

ENIAC used approximately 18 000 vacuum tubes, occupied 1800 square feet (167 square meters) of floor space, and consumed around 180 000 watts of electrical power. Punched cards served as the input and output; registers served as adders and as quick-access read/write storage.

The executable instructions composing a given program were created via specified wiring and switches that controlled the flow of computations through the machine. As such, ENIAC had to be rewired and switched for each program to be run.

Although Eckert and Mauchly were originally given a patent for the electronic computer, it was later voided and the patent awarded to John Atanasoff for creating the Atanasoff-Berry Computer.

Programs: Change The Software, Not The Hardware

Earlier in 1945, the mathematician John von Neumann demonstrated that a computer could have a simple, fixed physical structure and yet be capable of executing any kind of computation effectively by means of proper programmed control without changes in hardware. In other words, you could change the program without rewiring the system. The stored-program technique, as von Neumann’s ideas are known, became fundamental for future generations of high-speed digital computers and has become universally adopted.

The first generation of modern programmed electronic computers to take advantage of these improvements appeared in 1947.This group of machines included EDVAC and UNIVAC, the first commercially available computers. These computers included, for the first time, the use of true random access memory (RAM) for storing parts of the program and the data that is needed quickly. Typically, they were programmed directly in machine language, although by the mid-1950s progress had been made in several aspects of advanced programming. The standout of the era is the UNIVAC (Universal Automatic Computer), which was the first true general-purpose computer designed for both alphabetical and numerical uses. This made the UNIVAC a standard for business, not just science and the ­military.

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  • raclimja

    i still have my pentium 2 gathering dust on my closet

    improvements in technology is AMAZING
  • grooveboss
    ^ dweeb alert
  • Pyree
    The article contains no post-PC era nonsense! Just the way it should be.
  • dogman_1234
    I liked it. Love history; and the history of computerized technology. Can't wait to see the next 50 years.
  • mayankleoboy1
    just one question:

    why this article? in the whole wide range of PC, why this?
    you could have done the second part to the Antiliasing article.
  • cangelini
    mayankleoboy1just one question: why this article? in the whole wide range of PC, why this?you could have done the second part to the Antiliasing article.

    That's still on its way. It's very data-intensive and Don has been plugging away at it.
  • Chewie
    No mention of the Commodore in any of its forms? :(
  • SteelCity1981
    2006: Microsoft releases the long-awaited Windows Vista to business users. The PC OEM and consumer market releases would follow in early 2007:

    It should really read.

    2006: Microsoft releases the long-awaited Windows Vista to business users. The PC OEM and consumer market releases would follow in early 2007 and the vast majority of people quickly downgraded back to Windows XP:

  • madsbs
    Pics or it didn't happen!

    Where are the illustrations for this rather interesting piece?
  • jj463rd
    One thing that I disliked about the Timeline of Computer Advancements was leaving out Douglas Englebart and the Mother of All Demos in 1968(if you don't know about him you know very little about computer history )and giving accolades instead to Xerox.
  • Firehead2k
    I also missed the Commodore line of pcs
  • Mark Heath
    Nice read, reminded me to read up a bit more history on Apple, I knew jobs left for a while, but only found out today that he's apparently taken LSD and went Hindu after a trip to India. Yes, *apparently*, go look it up :)
  • molo9000
    he system’s $8975 price placed it out of the mainstream personal computer marketplace

    That's a mild understatement. In 1975 you could buy a brand new V8 powered Ford Mustang for $4000.

    The move to a PC-based architecture is without a doubt the smartest move Apple has made in years—besides reducing Apple’s component costs, it allows Macs to finally perform on par with PCs.

    Eh? Apple had to move to Intel because PowerPC was going downhill in 2006, but a there was a time when PowerPC chips were faster than Intel chips.

    I would say it is a safe bet that PC-compatible systems will continue to dominate the personal computer marketplace for the foreseeable future.

    That's a bold statement considering that the next version of Windows is going to be ARM compatible.
    The personal computer isn't going anywhere, but we might see the end of x86 dominance soon.
  • Krnt
    No Fusion and no ARM? WTF?!
  • nforce4max
    Where is Xerox and their contributions? They made the GUI and the mouse as well ethernet networking so it isn't like they were vaporware.
  • leandrodafontoura
    This article is misleading a little bit. Apple computers, before the change to Intel processors, used IBM processors, wich were significantly superior to Intel best solution
  • kilo_17
    So does this mean without IBM, the PC would be way different than what it is today?
  • ta152h
    Quite a few mistakes, but the most glaring is the overstatement with regards to the Apple II. What standard did it set? Expansion slots were on other machines, although IBM certainly saw this on the Apple. Of course, you didn't have the problems where certain card wouldn't work in certain slots (except in VERY rare cases), whereas Apple was much more rigid. The weird video where you couldn't put certain colors next to other colors were certainly never copied. The 6502 was a dead end, and Apple's next computer went to the 68K. The design where the keyboard was part of the computer was not copied by IBM,and in any case had been predated.

    Also, it was NOT a huge standard. The TRS-80 was at least as important in 1977 and the next few years, and was the best selling computer before the IBM PC came out. Also, don't forget Atari, which was also out there with the Atari 400 and Atari 800, and had very powerful video acceleration technology.

    It's not the Apple II wasn't selling, but it wasn't a predominate standard as stated, and had very strong competition. It was basically overpriced junk, with a slow, very annoying processor (which is the basis for ARM's instruction set), annoying video modes, weird floppy disk technology, and a price excessive for what the machine was.

    Also, the Pentium II was not basically a Pentium Pro with MMX. It had much more important changes (in retrospect, since MMX didn't matter much). For one, the Pentium Pro ran 16-bit code very poorly, and it was obscenely expensive because of the L2 cache on the processor package. They slowed down the L2 cache with external chips (for the Klamath, Deschutes, and Katmai), but doubled the L1 cache. This cut costs dramatically. Also, the Pentium II was able to run 16-bit code better than the Pentium for the first time.
  • jc5427
    No mention of Unix/Linux?
  • jcknouse
    They still make that book?

    I think I have the 2nd Ed of that book at home, with ISA ports listed in it.

    A free copy would mean I have one that's up-to-date. lolz
  • TeraMedia
    My father still has a working MITS altair. The disk drives are a bit flakey, and I don't think the punch tape drive has been used since the 70s, but it packs a full 64KB sRAM, and has switches on the front by which you can actually toggle in the machine code if you want. Working in 64 KB of program and data space is challenging to say the least. It runs a variant of BASIC written by William Gates, whoever that is.
  • cangelini
    madsbsPics or it didn't happen!Where are the illustrations for this rather interesting piece?

    Alas, we weren't able to add artwork to the story as it appears in the book; believe me, I wanted to as well :)
  • JohnA
    TA152HQuite a few mistakes....

    Yeah, I was going to add similar. One thing they also forgot was LIM, Lotus/Intel/Microsoft. Before MS put out the Office suit, and IBM headed down it's lonesome OS/2 trail (wow, not even a mention of OS/2 ???), Lotus played a role in the early evolution.

    What made the PC standard was open hardware, AND software the masses could use.
  • HistoryBuff44
    Im curious, why no mention of Konrad Zuse's Z1 machine he built in the late 30's and early 40's?