Computer Journey

This morning I found myself thinking about the computers I have used. When I was a young engineer, the first computer chips were invented and manufactured. They were called "microprocessors." When they became available to the public, I bought a printed circuit board that contained a microprocessor and auxiliary chips. The board was called the KIM-1, which I think stood for Keypad Interface Module or something similar. It was a learning tool to teach engineers about a particular microprocessor called the MOS Technology 6502.

KIM-1

The keypad in the bottom right corner was used to enter machine language instructions. Above the keypad were six 7-segment LEDs. The first four displayed a hexadecimal address, and the next two displayed a hexadecimal data byte. Hexadecimal numbers go from 0 to 15. The digits 0 - 9 are displayed in standard notation, and the digits representing 10 - 15 are displayed as A - F. If this confuses you, there is a ton of information on the Internet about hexadecimal math.There is also octal math, which uses only digits 0 - 7.

It accomplished its goal: to teach me about microprocessors, how they worked, what registers they contained, and the various addressing modes I could use to access memory. And it only cost $200. Of course, what you see in the photo is all you got. No power supply—I had to build that. No edge connectors either, I had to buy them. But there were two thick manuals that explained the processor, the MOS 6502.

Osborne One

A few years passed and the first "real" computer came along. This was the Osborne One. It had 64 Kbytes of memory, two floppy drives that stored 90 Kbytes each (92K if you counted the disk directory), and a 5 inch black-and-white, text-only monitor. The Osborne One ran the CP/M operating system. It also came with a thick user manual complete with source code for the BIOS (Basic Input Output System) and schematics for the computer board. Due to a health issue, I wasn't working at the time, but I had to have one. In 1982 I plopped down my last $1800 to buy one. I also bought a larger monitor (12"), and I made a little printed circuit interface board to connect the monitor to the Osborne. Later I converted the single density floppies to double density, and then each could store 180K of memory. The Osborne One used a Zilog Z-80 processor, and I got my hands on a Z-80 manual and studied all the op-codes and the addressing modes. I also got my hands on an assembler and linker, and I began writing "real" software that did useful stuff. I remember one program I wrote that simply installed a virtual drive onto the computer. It was a disk drive in memory. That is, it looked to the computer like another disk drive, but it was in RAM. Keep in mind I only had 64K RAM total, and 4K of that was dedicated to the video system, so I didn't have much memory to work with. The virtual drive was only 4K in size, not very useful, but it was the concept that I wanted to learn. I wanted to do it just to learn how to do it.

Along came the IBM PC with MS-DOS and changed everything. Other manufacturers began copying the PC and soon prices came down. When Windows 3.1 came along, I bought a PC clone. Then another, more powerful PC. Then a still more powerful PC. And I began teaching myself high level languages. Technology progresses, and at some point it becomes impossible to keep up with all the new stuff. It was time to let the young engineers choose from the new technology and carry on. I moved over to designing with Visual Basic, designing websites, and learning Javascript. But even with a more narrow focus, technology moves faster than a person can keep up with. 

Maybe I could keep up if I had a reason to do it. But I always learned for the pleasure of learning and for being able to do new and interesting things with what I learned. If we don't learn anything as we go through life, we might as well be daffodils.