keyboard curiosity

[Fran123]

Helly

That it is my cuiriosity:  what was the criterion for distributing the keys in each of the 10 lines?

Thank you

[Bryce]

If you mean "Why were the keys grouped in the rows / columns that they are in?", then it was most likely just to accommodate the easiest routing on the membrane.

Bryce.

[Prodatron]

Yes, that is/was the same for any system from the 1980ies.
They all used this 8bit x 10 (+/-...)row system, and it always depended on the membrane routing.
I only know about ONE system which did it in a very sorted way, and that was the MSX, as here they had to use the same key IDs for hundrets of different - but compatible- machines.

[Bryce]

Yes, that is/was the same for any system from the 1980ies.
They all used this 8bit x 10 (+/-...)row system, and it always depended on the membrane routing.
I only know about ONE system which did it in a very sorted way, and that was the MSX, as here they had to use the same key IDs for hundrets of different - but compatible- machines.

Most 8-Bit computers didn't have membranes, they had PCB's where the routing is a lot less limited: Commodore, BBC, Acorn, Atari and even the first CPC464's. Going to membrane was actually quite "cutting-edge" at the time! They had been used in calculators and a few other smaller devices already, but I think Sinclair were the first in the 8-bit scene? (Correct me if I'm wrong). Either way, it was quite a cutting edge (and risky*) move by Amstrad at the time.

Bryce.

*Risky: Membranes were a very new and relatively untested technology (for heavy usage) at the time. Amstrad were marketing the CPC as a potential business computer. If the membranes proved to be unreliable, they would have had a serious issue on their hands.

[Prodatron]

Most 8-Bit computers didn't have membranes, they had PCB's where the routing is a lot less limited: Commodore, BBC, Acorn, Atari and even the first CPC464's. Going to membrane was actually quite "cutting-edge" at the time! They had been used in calculators and a few other smaller devices already, but I think Sinclair were the first in the 8-bit scene? (Correct me if I'm wrong). Either way, it was quite a cutting edge (and risky) move by Amstrad at the time.

Bryce.

Interesting.
Anyway from all 8bit platforms I know the MSX is the only one, which doesn't have a "random" keyboard matrix, but a sorted one. Now I wonder how they realized this...

[rpalmer]

The reason for 10 rows was due to the decoder chip for the 4 binary select lines. The chip outputs 10 lines from 4-bits (0 to 9) and the scanning of each returns a byte. Thus we get 80 characters.

[Prodatron]

The reason for 10 rows was due to the decoder chip for the 4 binary select lines. The chip outputs 10 lines from 4-bits (0 to 9) and the scanning of each returns a byte. Thus we get 80 characters.

The most crazy thing with only 5 rows is still the ZX Spectrum. Only 40 keys at all, that's probably the negative record for an 80ies home computer. Writing a keyboard driver for this machine with all the advanced functions was really a challenge

[Bryce]

The reason for 10 rows was due to the decoder chip for the 4 binary select lines. The chip outputs 10 lines from 4-bits (0 to 9) and the scanning of each returns a byte. Thus we get 80 characters.

The most crazy thing with only 5 rows is still the ZX Spectrum. Only 40 keys at all, that's probably the negative record for an 80ies home computer. Writing a keyboard driver for this machine with all the advanced functions was really a challenge

And no matter how often I tried, I never got used to all those shortcut commands. It was a pain to program!

The Jupiter Ace also only had 40 keys, but the computer is so rare I've never seen one so I've no idea how it's laid out.

Bryce.