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Half a century later (guess what is 50 years old)

23 Apr 2024

Okay, I'll admit it... I'm old.

Hell, I'm even older than CP/M, the operating system that was a crucial part of the evolution of the microprocessor from a curiosity into the backbone of modern society.

Those of us who recall the early days of home computing will be able to recall an endless list of different computers that were totally incompatible. In the race to be "best" or to offer some unique benefit over their competition, manufacturers designed their own systems with little regard to compatibility.

In most cases, the only common thing shared by such systems was the BASIC language but even that varied widely from machine to machine. A BASIC program written for the Sinclair ZX80 would not run on a BBC Micro and nor would it run on an Commodore or an Apple without tweaking.

Once you bought a specific brand or even model of computer, you were locked-in.

Given that software was the key to turning these expensive home or small business computers into something useful, the lackof compatibility significantly slowed the growth of personal computing.

That all began to change when floppy disk drives became affordable and manufacturers started using an operating system to control such devices.

Although some computer makers rolled their own OSes (TRSDOS from Tandy for example), others who were using the 8080, 8085 or Z80 processors, decided to opt for a readily available "off the shelf" OS in the form of Digital Research's CP/M (Control Program for Microprocomputers).

Going with CP/M made sense for many computer manufacturers. It eliminated costly development work and gave them access to a growing library of titles that were specifically designed to run under the OS.

Even at a time when hardware standardisation was almost zero (the S100 bus notwithstanding), CP/M offered a glimpse of the future, where standards would become the backbone of the industry.

Around 1980 or so, a lot of different PC brands started appearing with roughly the same formula. They all had 8080, 8085 or Z80 processors, two floppy drives or a floppy and 5-10MB hard drive, 48 to 64K of RAM and an 80x24 CRT display. These machines ran CP/M and, with only a bit of tweaking in respect to the screen-control codes (ie: cursor positioning, clear-screen, etc), they could all run software written for the CP/M operating system.

Back in the very early 1980s, most of these machines sold for between NZ$4,000 and NZ$12,000 which, if you adjust for inflation, is between $20K and $60K in today's money.

Once CP/M gained a foothold in the small-business arena, those manufacturers relying on their own bespoke OS started to lose ground (with the possible exception of Apple). Pretty soon Commodore, Tandy and other early leaders started to falter and even big names, including Tandy had no option but to jump on the CP/M bandwagon for their small business offerings.

About this time the Osborne became a runaway success and I recall that despite the ludicrous price (about NZ$2,000 back in 1981 -- the equivalent of $10,000 today) and the tiny screen, these things sold like hotcakes, even after IBM released its PC around six months later.

Althought the low price was a factor, much of the Osborne's success can be attributed to the fact that it came with the CP/M OS and a bunch of really useful CP/M based applications including a word-processor, spreadsheet and database. There's no way they could have done this if the system was based on a bespoke OS.

So why am I writing about CP/M today?

Well because CP/M was first launched way back in the Northern autumn of 1974 which means that in a few short months, it'll be 50 years old.

This blog post gives a pretty good summary of the history of the OS and its founder, Gary Kildall. It's well worth a read.

Until I read this I wasn't aware by how many years CP/M predated my first involvement with microcomputers (about 1977) but it did bring back fond memories of countless hours spent using PIP, ASM, DDT and other system-level utilities on CP/M systems.

I also recall that although CP/M brought *some* standards to the world of 8-bit microcomputing, things such as RS232 serial communications, display terminals and floppy disk formats remained unique to almost each and every machine. So many frustrating hours spent trying to transfer files from "machine A" to "machine B" when they had incompatible disk formats and the serial port drivers were not interrupt-driven and thus limited to a few hundred bps, even if you could find a cable that worked. XModem, YModem and ZModem were the utilities of choice but not always available for every machine.

We've come such a very long way since those simple days but, when you think about it, it hasn't really taken that long.

almost 50 years ago I was hacking away with an 8080 assembler on an OS that took just a few Kbytes of memory on a machine with a 1MHz processor.

Today I'm using a powerful object-oriented language in an event-driven environment running on an OS that requires a couple of gigabytes of memory/storage and which zips along on a 3GHz multi-core processor.

Strangely enough... it takes me exactly the same amount of time to write a letter using a word-processing application today as it did all those decades ago.

Hmmm... isn't that food for thought.

Carpe Diem folks!

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