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Page references below refer to the Apple II Reference Manual, 1979 edition. As well as Integer BASIC itself, the following machine-language features were lost: The miniassembler (p.49), allowing one to type in 6502 opcodes that it would assemble into memory. (The format was the same as the monitor's L "list" command printed.) While it didn't support ...


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(It is assumed that this question is about the II or II+, not any later or third party model) TL;DR: Can the ] character really be generated on all unmodified Apple II (and Apple II+) keyboards with Shift-M? Yes. Are there any other "hidden" characters like this? Straight away no, but the original II and very early II+ keyboards (with MM5740 encoder)...


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The specific details of what a 6502 Apple II was doing when it was sitting at the BASIC command prompt or Monitor command prompt is this: Periodically check for a keyboard key press to be detected at address $C000 If no input, it runs a delay routine to display a blinking white box or a square checkerboard (later enhanced IIe ROM) as a cursor at the current ...


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I wrote some fairly deep systems code for the BBC Micro, a popular 6502 based machine. The OS for that machine struck me at the time as a lot more systematic than most of its 8 bit peers, in the sense of being well organised and a well thought out overarching design, but that was just my impression, it could be wrong. Ensure not only that a process can't ...


2

it doesn't seem clear to me how the operating system protects itself on the 6502 or PDP-11. With respect to the PDP-11: it's pretty conventional. In general, there are at least 2 execution modes (kernel, user; some models add a third, supervisor); certain instructions are legal in kernel mode only; there is a memory management unit that controls virtual ...


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I can't speak to the PDP-11, but the earlier PDP-10 was a computer built for timesharing. Memory protection was built into the processor. Every user mode memory reference went through a translation process controlled by two protection and relocation registers that in turn were controlled by the operating system. This memory system allowed the operating ...


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These computers were meant to be usable without a disk drive (which was sold separately and often cost as much as the computer did). DOS stood strictly for Disk Operating System and was just a way for the CPU to communicate with a disk drive. It wasn't an operating system in today's terms, which didn't come about until Mac OS and Windows took over in the ...


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I have done this with an 8051, (8 bit running about same speed as 6502) with a 4 task scheduler, driven by interrupts, task switching at about 10Hz. Reading position from NMEA on a GPS, sending and receiving GSM SMS messages, logging data to flash. No memory protection at all. Running in something like 1k RAM and 32k of ROM. Used a combination of ...


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