Back in the 1980s, a well-dressed man-about-town might have been carrying a simple digital diary like a CASIO SF-7500.
A couple of weeks ago, I was looking around a room at work that had been used as a bit of dumping ground. I found a few cables and telephones that I recovered for use elsewhere, and then I saw this box:
Intrigued, I checked inside and the diary was there, almost pristine, with a manual and a connection cable. It would not switch on, but I wondered if it worked. You will notice the date of 1989 on the display shown on the box, so this is what the well-dressed man-about-town would have been carrying in the late 1980s. The front of the box has a few details about what this machine could do, but then I turned the box over to discover a more fulsomely enthusiastic description boasting: "Massive memory, wide display, and world time function for the international businessperson!"
The unit and the front of the box tell us it has 64K of RAM. Now, the computers I played with in my youth -- Sinclair/Timex ones with a Z80 in them -- also had 16K to 64K of RAM. Modern tablet computers and smartphones, of course, have humongously more memory than this, but you have to start somewhere.
This device was capable of storing approximately 3,000 names and phone numbers. Let's say 20 characters per name and phone, multiplied by 3,000, is 60,000 characters, so that would be about right. When you are restricted to that amount of memory, of course, you'd probably write your software so it stores two numerical digits per byte, so you could store a 16-digit phone number in 8 bytes. And I notice from the sample displays that it only displays upper case letters, so you could probably make do with six or even five bits per character for the names. I wonder if it used techniques like this.
Looking at the manual, the unit required three 2025 coin cells for power. Two of these cells were for the main power while the third was for backup (so you wouldn't lose your data while changing the main batteries, I suppose). Obviously, even if the unit still functioned, all the cells would be long dead by now, but maybe it would still work if the batteries had not leaked all over everything.
Maybe I can clean it up and get it working again. In the meantime, did you ever own one of these devices (or something similar)? If so, are you aware of any techniques the designers used to compress the data and take maximum advantage of the limited resources?