No bugs in the first, smaller, version of the software (256 bytes of code blown into PROM by Nick Toop?s PROM blower). There were a couple of problems with the cassette interface software because I got the order of bits the wrong way round (from the CUTS? standard). But hey, it was only 512 bytes: you can?t make any mistakes in that even when you write it by hand, hand assemble it and hand enter it into the PROM blower! Besides, it could debug itself to a fair extent (given that it basically worked).
★ Cost-effective Resource Sharing
★ Support for common Services
★ Physical Layer
★ Data link Layer and
★ Network Layers
If the message is sent from a source to a single destination node, it is called Unicasting.
If the message is sent to some subset of other nodes, it is called Multicasting.
If the message is sent to all the m nodes in the network it is called Broadcasting.
Science of Cambridge used 8154s on its MK14 kit (National SC/MP based) and so they were available when we needed something for the 6502. They were fairly cheap and the extra RAM was a bonus, even though it meant converting from 6502 clock/write to the read strobe/write strobe that they used.
Packing them in boxes (upstairs at 4a Market Hill): the whole company would stand around tables (a production square) and put in the right components (me, Hermann, Hermann?s then fianc? Stephen, Chris). We all did pretty much anything: I ended up as Hermann?s secretary before we could afford one!
There used to be problems with answering the phone: one chap would ring up and say ?I have got an Acorn, it does not work? often enough for it to become a legend. We got very tired of kits ? the highlight being a guy who assembled his Atom with glue because he knew that heat (solder) would damage them ? so that coloured the BBC machine a lot.
Modifiable part of user space. May include program data, user stack area, and programs that may be modified.
The instructions to be executed.
Each process has one or more LIFO stacks associated with it. Used to store parameters and calling addresses for procedure and system calls.
Process control Block (PCB):
Info needed by the OS to control processes
Not exactly based on anything. Most of its heritage was from an automated cow feeder that I?d designed for a Harrogate company the previous summer (1977). Quite an advanced thing, really ? it had a (waterproof) number pad, big 7 segment LEDs, OS in non-volatile EEPROM, and the trademark 6502. Both were from my own designs for something for myself, and they came from the aether.
The most hair-raising thing was the cow-feeder?s programme. I didn?t own a PROM blower, so I had to write the whole thing by hand and send it off to a company who hand entered it into a machine and sent me back the PROM. That worked first time, too. Mind you, it was even smaller, being a boot loader that allowed the cow-feeder?s EEPROM to be initialised.