Page references below refer to the Apple II Reference Manual, 1979
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
(It is assumed that this question is about the II or II+, not any later or third party model)
Can the ] character really be generated on all unmodified Apple II (and Apple II+) keyboards with Shift-M?
Are there any other "hidden" characters like this?
Straight away no, but the original II and very early II+ keyboards (with MM5740 encoder)...
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 ...
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 ...
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 ...
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 ...
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 ...
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 ...