A Brief History of Computers

By Ed Dalton

Although various forms of calculating devices have existed for thousands of years, we don't normally think of such devices as computers. Generally, the word "computer," as it is currently used, refers to an electronic computer. The first electronic computers were built in the 1940s and 1950s. They used vacuum tubes and mechanical relays as switching elements. These machines were huge and generated a lot of heat. The vacuum tubes had short life spans, and had to be replaced on a continuous basis. Only governmental agencies could own computers of this type.

In the 1960s, computers began to use transistor circuitry, but they were still relatively large and expensive. A major business or a university could own one. Small businesses could still not afford computers of their own, but could sometimes rent time on computers, using remote terminals and modem connections. The computers of that period were known as mainframe computers.

During the 1960s and early 1970s, as the available transistor circuitry became smaller, the computers themselves (for a given level of computing power) became smaller and less expensive. The smaller computers began to be called minicomputers, to distinguish them from the larger mainframes.

During the 1970s, integrated circuits were invented. A single integrated circuit could replace hundreds of transistors, with great savings in size, power requirements, and cost. The integrated circuit that lay at the heart of the computer was called a microprocessor. Naturally, the use of integrated circuits made it possible to build computers that were small enough to fit on a desktop, and such computers came to be called microcomputers.

In the late 1970s, the cost of these desktop computers became low enough that individuals could own them. Of the earliest computers that were sold to the general public, there were two main types - those made by Apple, and those that used the S-100 bus and the CP/M operating system (made by about a dozen different companies). A typical computer of that period had 64K (65,536) bytes of memory. The displays were small (10 or 12 inch) monochrome character-based displays, and the printers (mostly daisy-wheel printers) were noisy and could not do graphics.

In the early 1980s, two major changes occurred. IBM released its first personal computer (called the IBM PC), and Apple released its first Macintosh computer. The Macintosh computer was quite extraordinary at that time, because it had a graphical user interface (GUI). It was the first computer sold to the general public that displayed information in windows.

Apple used a closed architecture, for which the components of an Apple computer were often unique, and only Apple manufactured computers with that architecture.

The first IBM PC had a floppy disk drive and an optional cassette recorder. It used an operating system called simply the Disk Operating System (DOS), and an Intel microprocessor called the 8088. Unlike Apple, IBM started out with many standard, off-the-shelf components. This led to a more open architecture, which enabled other companies to manufacture "clones" that were similar to the IBM PC. For this reason the IBM-compatible computer market grew much faster than the market for Apple computers. Microsoft sold an operating system for the IBM clones. It was called MS-DOS. The MS-DOS operating system allowed for up to 640K bytes of main memory (also called Random Access Memory, or RAM). Bill Gates is reported to have said at that time, "No one will ever need more than 640K bytes."

Soon after the first IBM PC came the IBM PC-XT, which had a hard disk, and could support tree-structured directories (folders). Then, in a steady succession, came the IBM PC-AT (using an 80286 processor), the 80386, and the 80486. People got tired of saying the "80" part, so they just started saying that they had a 386 or 486-based PC. After the 486 (where you might expect a 586) came the Pentium, the Pentium MMX (better for multimedia and high-speed graphics), the Pentium II, and currently the Pentium III.

In the 1980s, the Microsoft Windows operating system was introduced. This operating system gave the IBM PCs and their lookalikes (clones) a look and feel that was more like that of the Macintosh. The early versions of Windows were very slow and rather awkward compared with the Macintosh operating system. All through the 1980s the Macintosh was generally considered superior for publishing purposes, especially if a lot of graphics were used. It wasn't until the mid-1990s, with the release of Windows 95, that the IBM-style PCs came to be thought of as being on a par with the Macintosh.

The current generation of computers run at speeds of 300 to 500 Megahertz (MHz), compared with 4.77 MHz for the first IBM PC. An average amount of memory for a new computer might be 64 megabytes (MB), compared with 640 KB for the first IBM PC. That's 100 times as much memory. An average size for a hard disk might be 6 to 12 gigabytes, compared with 5 megabytes in the first IBM PC-XT. That's 1000 times as big a hard disk. Today's modems operate at 28K to 56K bits per second (baud) compared with 300 baud for the modems from the early 1970s. That's 100 to 200 times as fast.

Printers, meanwhile, have progressed from the noisy daisy-wheel printers, to the not-quite-as-noisy dot-matrix printers, to the very quiet inkjet and laser printers. You can get a very nice laser printer or photo-quality colour printer now for about one-tenth of what a daisy-wheel printer used to cost.

In general terms, if you multiply everything (processor speed, modem speed, amount of RAM, and size of hard disk) by 10 for each decade, you can get an idea of what personal computers will be like in the future. Meanwhile prices continue to drop. Nowadays, a handheld calculator costing less than $50 has the same computing power as a 1980 personal computer, costing back then upwards of $3000.

The preceding material was written by Ed Dalton. These are the opinions of the author, not the opinions of eBay, and therefore eBay does not validate the accuracy of or endorse these opinions.

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