Computers: Computer generations

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Computer generations

Another way of classifying computers is by generation.

• The first generation of computers were in operation in the 1950s, and their CPUs were built out of thermionic valves. As explained earlier, these computers were very large, expensive, and unreliable, and their performance was feeble by today's standards. (Today's computers are about a million times faster!) Also, they consumed a great deal of electricity and generated a lot of heat, so cooling systems had to be built in. Internal memory was by means of magnetic drums (similar in principle to today's magnetic disks), so memory access times were slow.

• The second generation were in operation in the early 1960s, the thermionic valves being replaced by transis­ tors (which at that time had to be soldered together rather than incorporated into a chip). These were smaller, cheaper, and more reliable than valves, and they consumed less electricity and produced less heat. They were about a thousand times faster than first­ generation computers. Internal memory was by means of core storage.

• The third generation came into existence in the mid 1960s, when microchips became available (consisting of many transistors and other components etched onto the surface of the chip). These were much smaller, cheaper, and faster than individual transistors soldered together. Processing times increased by a further factor of 1,000 at this time. Another characteristic of the third generation was the appearance of high-level programming languages such as COBOL and FORTRAN (see Chap­ter 4).

• Fourth-generation computers are characterized by chips exhibiting very large-scale integration (VLSI) of components. VLSI chips were developed at the start of the 1970s, and are, in effect, computers on a chip. Fourth­ generation computers are generally dated from the mid- 1970s, and include the current generation of microcom­puters. Various software innovations also characterize this generation, including systems network architecture and fourth-generation programming languages (see Chapter 4).

• The fifth generation is still largely on the drawing board, and is characterized by its ability to handle image recognition, speech recognition, and other artificial intelligence capabilities (see Chapter 5). Parallel pro­cessing techniques based on RISC chips (or their succes­sors) will be a feature of these computers.

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The evolution of the personal computer

Computers have been with us for less than half a century, yet they have transformed our world. The biggest change has taken place over the last 15 years, with the advent of fourth-generation computers, especially personal com­puters. There are now 40 million personal computers in use worldwide! Their impact has been so profound that it's worth devoting a few pages to their evolution.

The first microcomputers appeared in the mid 1970s.

They included the legendary Apple I and Apple II com­puters, and the Commodore PET. These computers were little more than toys by today's standards, endowed with a mere 16K of memory or less, storage by means of cassette tape, and low-powered 8-bit processors. Nevertheless they were cheap (by the standards of the day), easy to use, and you could use them to write letters and, if you were an enthusiast, to program.

What brought these computers to the attention of the business community was the appearance of a program called Visicalc. This was the world's first spreadsheet, and it was written for the Apple. It turned out to be just the kind oft hing that managers and decision makers needed (see Chap­ ter 6), and so large numbers of them bought the Apple just to run Visicalc.

The giant IBM manufactured only large computers at this time, and was reluctant to move into micros. One reason for this reluctance was the fact that micros on managers' desks threatened the power and the jobs of the people who actually purchased IBM's products, namely data processing personnel. Another was the destabilizing effect that such micros would have on IBM's large and profitable mainframe market.

However, by the start of the 1980s the highly successful Apple computer was making significant inroads into the business computing market, and IBM had to respond. In August 1981 it launched its first microcomputer, the original PC.

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The IBM PC

Technologically, the PC was no great advance on the older Apple and PET microcomputers. There were problems with the keyboard, the screen resolution was not all that good, it had only 64K of memory, and the operating system (DOS) was simply a rehash of the older CP/M operating system. The reason for the PC's remarkable success was the badge on the front that said 'IBM'.

At that time IBM dominated the computer market to a much greater extent than it does today. It offered its customers a coherent range of products, with a natural upgrade route from less powerful to more powerful and from older to newer. It offered them maintenance and other support, and it offered them the security of dealing with a supplier who, without doubt, was not going to collapse and disappear. Apple Computing, however good its product, could offer none of these benefits- although, in retrospect, it has not disappeared and in the second half of the 1980s enjoyed a marked increase in popularity and profitability.

IBM's entry into the microcomputer market provided just the push that commerce and industry needed to embrace this most important component of the information tech­nology revolution. Companies were prepared to buy the PC because the IBM badge gave it credibility. Software houses were prepared to write packages for it, because there was a large and growing market. More people were prepared to buy the PC because of this growing range of software, and this encouraged yet more software houses to enter the fray. An exponential growth set in, with ever more customers buying and ever more and better software being sold, to the benefit of all. The PC had set the industry standard for producers and users, and the microcomputer had come of age.

But this benign circle of users and software producers was not the only reason for the wholesale adoption of the PC. Another factor helped to fuel the boom, one which IBM had built into its computer without realizing where it would lead.

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