It was actually September 1977 when the Cambridge Programmable came out. I bought one at the time, and can still remember my frustrations of trying to use the thing for basic college maths, like the fact the trig functions only worked in radians, and our work was all in degrees. Which meant one had to constantly use the R>D keys and D>R keys for every calculation. After a few weeks of this, I replaced it with a Casio FX-41 for my college work. As the battery cover has that kludge pregnant bulge in it, to accommodate PP3 9V batteries. It did originally come with a cradle, so it could be used on a desk without it wobbling around and having to hold it. Originally the Cambridge series of calculators ran on 4 AAA batteries, for 6V, which was what the case moulding was designed for. But as the NS chips require 9V to operate, Sinclair had to bodge the thing in their typical style.

My first business was making these from kits for my school-mates! I was about as profitable as Sinclair, mainly because only around 50% were functional and it was not my soldering at fault. They always replaced them without comment so I am fairly sure they were pushing chip quality control onto customers! I also vividly remember the customer complaints about the inaccuracy of the trig functions (I could forgive a four-digit precision limit if it did not make up a further four digits at random)!

Hey man, your channel is somewhat obscure on KZfaq since there aren't many people who enjoy calculators nowadays. But I love it, please keep doing those really nice videos, I've watched by now nearly all of them.

Sinclair bought me so much happiness growing up , I had all the latest sinclair products and everyone on my street wanted to play on my zx spectrum and my brother and me learned coding together and it lead to both of us becoming integration developers

Don't know what happened to my comment! Anyway, I bought one of these for £12 in 1979 (I was 12!) and never stopped buying 9v batteries for the damn thing. It was my introduction to computing, but even then I knew it was crap. The accuracy was terrible, and the on/off key wore out quickly. Nevertheless it got me into the game. Like all Sinclair products, it was a bodge. The calculator chip was never meant to do anything more than function as a simple calculator, but as usual, uncle Clive managed to make it do something else. Something more than it ever should have done. The 36-step program memory, was, if I remember correctly, just 18 bytes. Each step took one nybble (4 bits). My next calculator was an HP41C.

Battery life on these was like 20 minutes. No ability to save programs and no wall plug in. By the time you keyed in a long program, you would have about 5 minutes of run time. I rigged up a 9 volt DC wall transformer with alligator clamps so I could run it all day. This eventually burned it out. It was an interesting bit of tech for 1977. But its input methods just drove me crazy.

Oh man, I want to see one of these overclocked!

Thanks for the video! Memories! I was in high schhol and got this one in 1977. It was my first calculator. I recall loading a lunar lander program on it. I went to the TI 58 a couple of years later upon starting as an engineering freshman.

I still have mine, and a number of programs I wrote back then (that must have been 1979 I guess). I was living thousands miles away and have been reunited with it just a few months ago when I moved back home. However, I don't know if it still works. I have not tried to put a battery in it, yet.

The Texas Instruments SR-52 supported algebraic precedence in 1976. TI-58/59 supported algebraic precedence in 1977 (see 3 min 17 sec into the video)

It'd be great if you posted on LBRY!

The Casio FX39 was not the first to have algebraic precedents in 1978...The TI SR50 of January 1974 had it.

What's confusing is how 2 + (3 x 4) managed to equal 12.000000 @6:43 I think that you needed to hit the "=" key. :) Nonetheless, great video and I may have to pick one of these units up. Thanks!