Chances are, you’re reading this on a “PC”. A few years ago this meant a Windows-based system, but anything that uses the x86 architecture is technically an “IBM Compatible PC”, including those Linux-based netbooks and even modern Intel Macs. But do you know where the “PC” designation actually comes from?

Let’s start at the beginning. In the 1970s, the mainframe reigned supreme. In most cases, your monochrome ‘dumb’ terminal (meaning that it had no processing capability of its own, let alone disk drives) was connected to the a DEC PDP-10 or IBM System/360, which usually featured a multi-user UNIX operating system and a large bank of hard disk drives used to store all of your files. Computer usage was restricted to the military, large companies and universities.

That was soon to change, however. In 1977 the Apple II (pictured above) was released, the first hugely successful self-contained ‘desktop’ system – so successful, in fact, that Apple continued to manufacture it until 1993. It featured 4KB of RAM and a MOS 6502 CPU running at 1MHz. Up until 1981, the Apple II was the closest the world had to a standardised ‘personal’ computer, although the market was still largely segmented due to the success of the TRS-80 and the Commodore PET.

In 1980, however, mainframe giant IBM decided that they wanted in on the action. The result was the August 1981 release of the PC 5150, using Intel’s 8088 CPU running at 4.77MHz and packing 64KB RAM. Thanks to IBM’s well-known and respected name in the mainframe industry, as well as the system’s notoriously high build quality compared to its rivals, the PC caught on quickly and started to appear on office desks all over the world.

The IBM featured 5 8-bit ISA expansion slots, and with an uprated power supply could also support an internal 10MB Hard Disk. Depending on configuration (and there were many, many options available), the system could support TV output, serial and parallel communication, networking, colour graphics and even sound. ISA slots became an industry standard supported well into the late 1990s.

The PC family continued with the PC/XT and the PC/AT. The AT is particularly important because it gave us the AT motherboard standard, variants of which are still used to this day.

As clones of the IBM machine started to appear, the term “IBM Compatible PC” became popular as a marketing term, covering systems that shared the PC line’s Intel processors (most importantly the 286 and later 386), rear connectors, ISA bus and support for PC-DOS, which later became MS-DOS. The hardware and software standardisation that we still enjoy today enabled hardware and software companies to focus their attention on one type of system, which certainly made their lives a lot easier.

Even throughout the early 90s competition to the IBM PC standard was still enjoying great success, with the Apple Macintosh line, Atari’s ST, and Commodore’s Amiga being the most notable. Unfortunately this interesting variety has now faded into obscurity, even modern Apple computers are based on the x86 architecture pioneered by those early IBM desktop machines.

So next time you describe yourself as a “PC user” you can truly appreciate the what is really means!

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