The 10 most influential computers in history

8th Aug 2010 | 09:00

The 10 most influential computers in history

The machines that shaped the information age as we know it

The 10 most influential computers in history

Some people view the digital revolution as being just a little over 50 years old – but the fact is, today's most powerful computers are the result of decades, centuries and even millennia of development.

At the beginning of the story, you could argue, we humans counted with our fingers, and from that clumsy process the Intel Core i7 was eventually born.

To explore the genesis of the computer we set ourselves a task. We wanted to warp back to the very earliest days of computing and track our way through to today. As we walked through the ages, we wanted to identify the most influential computers – machines that shifted the course of computing forever. So, come with us as we visit the most influential computers ever made.

1. The abacus

OK, so the abacus was hardly a computer, but we really can't start our journey anywhere else but here. This ancestor of all mechanised computing aids was first used in Samaria and dates back to before 2,000 BC. A variant is still in use in the Far East today.


In its usual form, the abacus has several rods – each of which represents a power of 10 – onto which beads are threaded so that they're free to slide up and down. If you want to get a hands-on view of how this mechanism assists people with simple arithmetic, take a look at the JavaScript abacus.

While all fell short of what we'd now consider a computer, various arithmetic devices were introduced over the next the two millennia, some of which remained with us until the 20th century.

One abacus descendant is the slide rule. This was an analogue calculating device based on logarithms, and it was famously used by a bunch of boffins in the 1950 BBC election broadcast to calculate the swing as each result came in.

The mechanical adding machine, on the other hand, was a common piece of office equipment until it was replaced by the electronic calculator in the 1970s.

2. Babbage's Difference Engine

An abacus, a slide rule or an adding machine could each be used to perform a single calculation. Babbage's Difference Engine was quite different. It was intended to perform a series of calculations.

Designed between 1847 and 1849, it was never actually built in Babbage's lifetime. In 1991, however, the London Science Museum built a model to Babbage's original plans. It worked perfectly.

Difference engine

Although it was a purely mechanical machine, driven by a crank handle and containing cogs, gears and levers, it accurately calculated and printed tables of polynomials that were used for astronomy and ballistics.

Next came Babbage's steampowered Analytical Engine. Unlike the Difference Engine, which was designed to perform a particular type of computation, the Analytical Engine was a programmable or universal computer in just the same way as today's PCs. Indeed, programs written for it by Babbage's contemporary Ada Lovelace bear an uncanny similarity to modern computer programs.

Add all this up and you could argue that the Analytic Engine represents a more significant step than the Difference Engine did. The problem was that the Analytic Engine was never built by anybody, and so the machine remains largely untested.

3. Colossus

The first completely electronic computer Like Babbage's Analytical Engine (which is best described as a calculating machine), Colossus was a proper computer, albeit one that was designed to perform one very specific type of calculation.

Where it broke new ground was that, for the first time, it was purely electronic. Created by Tommy Flowers and his team at the Post Office Research Station in 1944, it was used at Bletchley Park as part of the World War II code-breaking effort.


While a mechanical computer called the Bombe had been adequate to crack messages encrypted using the famous Enigma machine, the more complicated German Lorenz cipher machine that was used to encode teleprinter traffic required the increased speed of an electronic computer in order to break the code.

Colossus contained no less than 2,400 valves. With memory being expensive, the data was operated on directly from paper tape. As a result, the speed of the computer depended on the speed of the tape reader.

Operating at 40 feet per second (27.3mph), Colossus had a speed of 5,000 characters per second. A rebuilt Colossus is now on show at the National Museum of Computing at Bletchley Park.


Designed and built at the University of Pennsylvania under a US government contract, and intended for nuclear weapons research, ENIAC became the world's first 'universal' electronic computer: in other words, one designed to do any job according to its programming.


It was completed in 1946, and its headline figures are startling. It contained 17,468 valves, 7,200 diodes, 1,500 relays, 70,000 resistors, and 10,000 capacitors, all held together by about five million hand-soldered joints. It weighed 27 tonnes, measured 2.6m x 0.9m x 26m, and consumed 150kW of electrical power. When translated into today's terms, it set Uncle Sam back about $6million – and that's not including the power bill!

Despite being the first universal computer, ENIAC differed in several important respects from its various successors. For a start, it operated on decimal rather than binary arithmetic, something that contributed massively to the valve count – which was huge, given its rather pedestrian performance.

More significantly, despite being universal in nature, ENIAC was programmed by plugging patch leads and configuring switches. As a result, changing the machine's configuration from one operation to another was a task that would typically take several days to complete – a far cry from the simple speed of loading a program from disk that we're used to today.

5. The Manchester Baby

The Small Scale Experimental Machine (SSEM), or Manchester Baby, was completed in 1948. It was dubbed Baby in an effort to differentiate the machine from its successor, the Manchester MK1.


The SSEM was groundbreaking. Here was a computer that was fully electronic, truly universal and, for the first time, could execute a program stored in internal memory. As it was the first ever stored program computer, we are able to draw some direct comparisons between the Manchester Baby and today's PCs.

It had 550 valves (transistors, integrated circuits and microprocessors were still some way off), and just seven instructions, which could be executed at a rate of 700 per second. It had 32 words of 32-bit memory.

Although you'd have to put several zeroes on the end of these figures to come close to describing today's PCs, it's fair to say that the world owes a debt of gratitude to SSEM's creators Freddie Williams and Tom Kilburn of the University of Manchester.

IBM System/360, DEC PDP-8 and more

6. IBM System/360

Even by the early '60s, a dozen years after the pioneering SSEM, computers were still most definitely for the few rather than the many. IBM, which had entered the computer market back in 1953, was about to change all that.

IBM system/360

The IBM System/360 was launched in 1964, and is considered by some to have been the most successful mainframe computer of all time. The System/360 had a 32-bit architecture, something that didn't make its appearance in the PC market for another 21 years. Although few companies could afford to fully populate them, some models could take up to 4MB of memory.

Perhaps the main attraction was that software developed for any model would run on any other, thereby permitting an upgrade path.

IBM soon emerged as head and shoulders above the competition, and went on to dominate the mainframe market for decades. Viewed in the light of today's computers, a System/360 would appear huge. Each component – the CPU, the disk drives, several tape drives, line printers and an operator's console – was housed in its own cabinet, which meant that a system would occupy a whole room, which would need to be both fairly large and well air-conditioned.

7. DEC PDP-8

Despite the success of the IBM System/360, mainframe computers still remained the sole domain of moneyed government departments, universities and large corporations. Generally leased rather than bought, these machines could set their owners back a million dollars a year.

DEC pdp-8

The computers would also need a team of operators to care for the machines, further pushing up costs. By the early 1960s, the race was on to downsize the computer and, in so doing, make computing accessible to smaller organisations.

While other companies may have created mini-computers first, the first firm to really break into this embryonic market was Digital Equipment Corporation (DEC). Introduced in 1965, DEC's PDP-8 was the first mini-computer to sell in significant numbers. It was sold for a fraction of the price of even the smallest IBM System/360 mainframe.

The CPU was about the size of one of today's large PCs, and when the storage and other peripherals were added, the whole computer was about the size of a domestic fridge. Most importantly, it could be operated by the people who needed to use it. It never sold as many as its successor – the hugely popular PDP-11, which was launched in 1970 – but that doesn't change the fact that the PDP-8 got there first.


Such was the magnificence of the PDP-8 and the mini-computer era it pioneered that it took a whole 16 years for the next true hero of computing to come along. There were some noteworthy efforts in the interim – the Apple II and the Commodore PET – but they were all overshadowed by the IBM 5150.

IBM pc

This pioneering machine was launched in 1981 and it kick-started the desktop PC revolution. Indeed, your desktop PC of today is very much its direct descendant.

At the time, commercial success wasn't exactly assured, because the 5150 was massively expensive. The original 1981 PC sold for $1,565, which would be the equivalent of $3,900 (or £2,600) today!

Despite these wallet-wilting features, the machine had a very sparse specification. For example, it didn't come with a monitor: you had to use a TV. It had 16kB of memory and, as hard drives were squarely a thing of the future, you had to make do with floppy drives. Even these were an optional extra – IBM intended 5150 machines to store data on cassette tapes.

9. Sinclair ZX81

If imitation is the sincerest form of flattery then IBM must have been over the moon at the appearance of the many clones of its PC that soon flooded the market. Although the following wave of lookalikes succeeded in forcing prices down, back in the 1980s the PC was still most definitely a tool for businesses only.

Sinclair zx81

The machine that changed all that, at least here in the UK, was the Sinclair ZX81, which is still remembered for its super low price. On its launch it took the country by storm. It might have looked more like an overgrown calculator with its primitive membrane keyboard, but it cost just £69.95 (or £49.95 if you were prepared to solder the components onto the circuit board yourself).

Sinclair managed to keep the ZX81's price low by reducing the number of chips on the motherboard from 21 on the ZX80 to four on the ZX81.

Needless to say, the ZX81 didn't pack the same sort of punch as the IBM PC. It had an 8-bit Z80 processor with a clock speed of 3.25MHz, 1kB of RAM, and featured monochrome output to a TV set. The display comprised 24 lines of text, each 32 characters long or, in block graphics mode, it provided a resolution of 64 x 48 pixels. Oh, and you had to use a cassette recorder for storage.

10. Apple Mac

The computer that brought us a GUI and mouse No, you haven't opened a copy of MacFormat by accident: even a dyed-in-the-wool PC user would have to admit that the Apple Macintosh was groundbreaking when it first appeared back in 1984.

Apple mac

Today its all-in-one appearance looks somewhat quaint, but it had one very important thing going for it that wouldn't emerge into the PC world for another eight years. When PCs were still driven by entering cryptic commands at a prompt on a text display, Apple Mac users were clicking graphical icons on-screen and having information presented to them in windows.

Here was the first mass-produced computer to be shipped, as standard, with a graphical user interface and a mouse – and the computer industry has never looked back. While touchscreens and voice input have been hyped as the next breakthrough in user interfaces, this concept is alive and well over a quarter of a century on.


First published in PC Plus Issue 297

Liked this? Then check out Getting connected: a history of modems

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