Last month at the Federal Computer Conference, they had key-note address on the 10th anniversary of the IBM PC. On a big screen monitor they played those old IBM Charlie Chaplin advertisements.
This started me thinking and it dawned on me that this year was the 10th anniversary of the Sinclair ZX-81. The ZX-81 was introduced 1n England on March 1981 and introduced to the U.S. at a press conference in Boston on Oct. 7, 1981.
I first saw mention of the ZX-81 1n an issue of Popular Science. They had a short blurb on the ZX-81 when it was intro’d in England. Later I saw an add for the ZX-81 1n the October issue of Popular Science. At that time I was looking at the various computers on the market. I was leaning toward the VIC-20 which cost $400. When I saw that the ZX-81 would cost me $250, including 16K, I quickly rushed off a check to Sinclair.
I received my ZX-81 the day before Thanksgiving. When my Step-Father first saw it he said “You paid $250 for that?” Indeed it did look small. I spend most of Thanksgiving booking it up to the TV and trying it out.
My first attempts on the ZX-81 were not too successful. For some strange reason I could not load any programs that I had saved. I could hear the sound of the programs, but they would not load. I finally fixed the problem when I discovered that you had to push both the play and record buttons on the tape player. I had been pushing record only, just like the tape player on my stereo.
Since I was new to programming i picked up David Ahl’s two books “101 Computer Games” and “More Computer Games. ” Just reading the programs helped me learn BASIC.
After I found out about Sync Magazine, I subscribed to it and it very informative and provided even more programs to learn off of.
The ZX-81 is a great computer to learn on. Its whole operation is fairly simple. After I learned BASIC, I started playing with some of the internals of the computer. I found a few system variables that could be used for a few tricks.
I then moved on to assembly language. Toni Baker’s book on machine code helped me get over the hurdle. Since the ZX-81 1s simple, writing assembly programs were fairly easy. With other computers you must work with the operating system, but on the ZX-81 you have total control of the computer.
1 picked up a copy of the ZX-81 ROM disassembly and found a few ROM calls that I could use to save writing my own code. If I ever get back into assembly programming. I will probably bring my ZX-81 (or T/S 1000) out of retirement. It really was fun to hack on.
One of the neatest programs saw for the ZX-81 that was called AUDISEY by Ron LeMon, published Sync. It was a machine code routine that would sample and store sounds from the cassette port. After storing a few seconds of sound the program could play back the sound. In a way it worked like a sound digitizer. Very creative use of the cassette port. I still have the issue Sync if anybody is interested.
I like programming on the ZX-81 because the display quality was limited. The better the screen display the more work you have to put into the physical presentation of the program. It would only take minutes to work out a fairly good looking ZX-81 screen, but on the QL, it can take hours to get everything right.
I have many fond memories of spending hours sitting at the keyboard of my ZX-81 (so much that I wore the keyboard out). The ZX-81 was designed to be a learning tool. Simple to build and program. It achieved that goal remarkably. It is simple enough for students to know in and outs of the computer, from the low level hardware all the way to programming it.
In another 6 to 10 years I plan to introduce my new daughter to computers thought the ZX-81. It was first and I want it to be her first. I hope she finds computers as fascinating as I do.