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I am not stupid, you know. They cannot make things like that yet.

20 November 2009 21:50

I've really enjoyed reading some of Matthew Garrett's entries about legacy PC hardware features - specifically the cute hack involving A20 and the keyboard controller. Reading things like that really takes me back.

I remember when the z80 was cutting edge, and I discovered you could switch to a whole new set of shadow registers via "exx" and "ex af,af'". I remember using undocumented opcodes, and even now I can assemble and disassemble simple z80 machine code. (Don't get me started on the speedlock protectors and their fiendish use of the R register; that'll stick in your mind if you cracked it. I did.)

I remember being introduced to the PC, seeing subdirectories appear in MS-DOS 2.0, network redirectors appearing in DOS 3.x, and support for big hard drives appearing in MS-DOS 4.0.

I remember the controvosy over the AARD code in the betas of Windows 3, and the focus that was given in the book "Undocumented DOS" which mostly focussed upon the "list of lists". (At that time I'd have been running GEM on an IBM XT with hercules (monochrome) graphics.)

I remember learning about that a .COM file was a flat image, limited to 64k which loaded at offset 100h, to accomodate the PSP (program segement prefix) for compatbility with CP/M (something I've never seen, never used, and known nothing about. I just know you could use the file control blocks to get simple wildcard handling for your programs "for free")

I wrote simple viral code which exploited this layout, appending new code to end of binary, replacing the first three bytes with a jump to the freshly added code. Later you could restore the original bytes back to their original contents and jump back to 100h (I even got the pun in the name of 40Hex magazine.)

I recall when COM files started to go out of fashion and you had to deal with relocation and segment fixups. When MZ was an important figure.

I even remember further back to when switching to protected mode was a hell of tripple-faults, switching back from protected mode to real mode was "impossible" and the delight to be had with the discovery and exploitation of "unreal mode".

All these things I remember .. and yet .. they're meaningless to most now, merely old history. Adults these days might have grown up and reached age 20 having always had Windows 95 - never having seen, used, or enjoyed MS-DOS.

How far have we come since then? In some ways not far at all. In other ways the rise of technology has been exponential.

Back then when I was doing things I'd not have dreamed I could update a webpage from a mobile phone whilst trapped upon a stalled train.

There are now more mobile phones than people in the UK. In some ways that's frightening - People miss the clear seperation between home & work for example - but in other ways .. liberation.

I have no predictions for the future, but it amazing how far we've come just in my lifetime; and largely without people noticing.

The industrial revolution? Did that happen with people mostly not noticing? Or was there more concious awareness? Food for thought.

ObFilm: Terminator

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The selfish programmer

25 July 2014 21:50

Once upon a time I wrote a piece of software for scheduling the classes available to a college.

There was a bug in the scheduler: Students who happened to be named 'Steve Kemp' had a significantly higher chance (>=80% IIRC) of being placed in lessons where the class makeup was more than 50% female.

This bug was never fixed. Which was nice, because I spent several hours both implementing and disguising this feature.

I'm was a bad coder when I was a teenager.

These days I'm still a bad coder, but in different ways.



Growing food is fun.

27 July 2020 12:00

"I grew up on a farm" is something I sometimes what I tell people. It isn't true, but it is a useful shorthand. What is true is that my parents both come from a farming background, my father's family up in Scotland, my mother's down in Yorkshire.

Every summer my sisters and myself would have a traditional holiday at the seaside, which is what people do in the UK (Blackpool, Scarborough, Great Yarmouth, etc). Before, or after, that we'd spend the rest of the summer living on my grandmother's farm.

I loved spending time on the farm when I was a kid, and some of my earliest memories date from that time. For example I remember hand-feeding carrots to working dogs (alsatians) that were taller than I was. I remember trying to ride on the backs of those dogs, and how that didn't end well. In fact the one and only time I can recall my grandmother shouting at me, or raising her voice at all, was when my sisters and I spent an afternoon playing in the coal-shed. We were filthy and covered in coal-dust from head to toe. Awesome!

Anyway the only reason I bring this up is because I have a little bit of a farming background, largely irrelevant in my daily life, but also a source of pleasant memories. Despite it being an animal farm (pigs, sheep, cows) there was also a lot of home-grown food, which my uncle Albert would deliver/sell to people nearby out of the back of a van. That same van that would be used to ferry us to see the fireworks every November. Those evenings were very memorable too - they would almost always involve flasks of home-made vegetable soup.

Nowadays I live in Finland, and earlier in the year we received access to an allotment - a small piece of land (10m x 10m) for €50/year - upon which we can grow our own plants, etc.

My wife decided to plant flowers and make it look pretty. She did good.

I decided to plant "food". I might not have done this stuff from scratch before, but I was pretty familiar with the process from my youth, and also having the internet to hand to make the obvious searches such as "How do you know when you can harvest your garlic?"

Before I started I figured it couldn't be too hard, after all if you leave onions/potatoes in the refrigerator for long enough they start to grow! It isn't like you have to do too much to help them. In short it has been pretty easy and I'm definitely going to be doing more of it next year.

I've surprised myself by enjoying the process as much as I have. Every few days I go and rip up the weeds, and water the things we've planted. So far I've planted, and harvested, Radish, Garlic, Onions, and in a few more weeks I'll be digging up potatoes.

I have no particular point to this post, except to say that if you have a few hours spare a week, and a slab of land to hand upon which you can dig and plant I'd recommend it. Sure there were annoyances, and not a single one of the carrot-seeds I planted showed any sign of life, but the other stuff? The stuff that grew? Very tasty, om nom nom ..

(It has to be said that when we received the plot there was a jungle growing upon it. Once we tidied it all up we found raspberries, roses, and other things. The garlic I reaped was already growing so I felt like a cheat to harvest it. That said I did plant a couple of bulbs on my balcony so I could say "I grew this from scratch". Took a while, but I did indeed harvest my own garlic.)

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