Hi,
Nines' complement and ten's complement are to decimal what ones' and
two's are to binary, i.e. you can subtract a number by adding its ten's
complement instead. Old adding machines would have nines' complement
digits written alongside the normal digit, e.g. 2 by 7.
https://en.wikipedia.org/wiki/File:Comptometer1920Model.jpg
https://en.wikipedia.org/wiki/Method_of_complements
I've been reading this book, about half-way through so far, and it seems
ideal for someone that wants to understand how computers work. It
starts with sending Morse code with torches and builds from there,
through logic gates, implementing arithmetic, counters, memory, assembly
language, and finishes off by touching on some real CPUs, character
encodings, what an operating system does, and floating point numbers.
I'd guess reading age could be a bright twelve-year-old upwards.
Code: The Hidden Language of Computer Hardware and Software,
by Charles Petzold https://amzn.to/2J7FEjb
Nick is considering Manjaro Linux instead of sticking with Kubuntu or
moving to Xubuntu. It's a rolling release distro, so no `upgrade the
world' periodic shock, based on Arch Linux, but with a graphical
installer, and a delay between a package being in Arch's `bleeding edge'
`stable' and it making it to Manjaro's `stable'.
https://en.wikipedia.org/wiki/Manjaro_Linux
Cheers, Ralph.
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